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The objective of this study was to identify the nitrogen oxide form(s) involved in the functional impairment of the rat taurine transport system. Taurine uptake activity in the rat renal brush border membrane vesicle (RBBMV) preparation or Xenopus laevisoocytes that express the rat taurine transporter was compared after the pretreatment with nitrogen oxide donors from which nitric oxide (NO) is released at different rates. The functional impairment was associated with a reduced Vmax, but did not involve an alteration in the Km, of taurine uptake in the RBBMV preparation that had been pretreated with sodium nitroprusside, a slow release nitric oxide (NO) donor. When the preparation was pretreated with S-nitroso- N-acetyl penicillamine, a rapid release NO donor, the activity of taurine uptake was unaffected. The activity was not statistically different from the control after the pretreatment with sodium nitroprusside and superoxide dismutase. Consistent with the study with RBBMV, a similar alteration in the activity of taurine uptake by NO donors was observed in oocytes expressing the transporter. Considering the fact that peroxynitrite, a highly reactive nitrogen oxide form, is formed by the reaction between NO and superoxide, the taurine transporter, and probably other transport systems as well, may be functionally impaired by peroxynitrite.

The objectives of this study were to evaluate the relative contribution of the direct pathway in overall brain transport for 17 model drugs with different physicochemical properties after nasal administrations and to identify factors that govern the fraction of the dose transported to the brain via the direct pathway (Fa direct). When the model drugs were nasally administered to rats, 5 of the 17 model drugs were delivered to a significant extent to the brain via the direct pathway. Multiple linear regression analyses showed that the correlation between various physicochemical properties and Fa, direct was not statistically significant, indicative of a lack of primary physicochemical determinants in the direct transport pathway. Transporters such as rOAT3 and rOCT2 were expressed at significant levels in rat olfactory epithelia, and uptakes of standard substrates were significantly decreased in HEK293 cells expressing rOAT3 and rOCT2 in the presence of the five model drugs that were delivered to appreciable extents to the brain via the direct pathway. Therefore, these observations indicate that carrier-mediated transport may play a role in the brain delivery of drugs from the nose via the direct transport pathway.

The objective of this study was to investigate the transport kinetics of cyclosporin A, a well known substrate for P-glycoprotein (P-gp), across the blood-brain barrier (BBB), and the expression of the transporter in the brain of streptozotocin-induced diabetic rats. The in vivo transport clearance of cyclosporin A was significantly reduced in diabetic rats compared with that in the control. The decreased transport was associated with the increased level of mRNA and the protein for P-glycoprotein in the rat brain. The functional activity of the efflux transporter in mouse brain capillary endothelial (MBEC4) cells, an in vitro model of the BBB, was also stimulated when slow nitric oxide (NO)-releasing donors were present, whereas the stimulation was absent in the case of rapid NO-releasing donors (e.g., S-nitroso-N-acetyl-dl-penicillamine and diethylenetriamine). The stimulatory effect was highest for sodium nitroprusside (SNP) and the functional induction associated with the increased mRNA and protein level of the transporter. The pretreatment of the cell with SNP along with ascorbate, methylene blue, or superoxide dismutase attenuated the induction of function and expression for P-glycoprotein, suggesting that the reaction product between superoxide and NO is involved in the induction of function and expression. The level of nuclear translocation of nuclear factor-κB (NF-κB) and DNA binding activity of nuclear extracts to the NF-κB consensus oligonucleotide was increased in MBEC4 cells pretreated with SNP. Taken together, these observations suggest that nitrosative stress leads to the up-regulation of the message for the efflux transporter and, ultimately, to the enhanced function, probably via a NF-κB-dependent mechanism.

The objective of this study was to investigate the transport kinetics of cyclosporin A, a well known substrate for P-glycoprotein (P-gp), across the blood-brain barrier (BBB), and the expression of the transporter in the brain of streptozotocin-induced diabetic rats. The in vivo transport clearance of cyclosporin A was significantly reduced in diabetic rats compared with that in the control. The decreased transport was associated with the increased level of mRNA and the protein for P-glycoprotein in the rat brain. The functional activity of the efflux transporter in mouse brain capillary endothelial (MBEC4) cells, an in vitro model of the BBB, was also stimulated when slow nitric oxide (NO)-releasing donors were present, whereas the stimulation was absent in the case of rapid NO-releasing donors (e.g., S-nitroso-N-acetyl-dl-penicillamine and diethylenetriamine). The stimulatory effect was highest for sodium nitroprusside (SNP) and the functional induction associated with the increased mRNA and protein level of the transporter. The pretreatment of the cell with SNP along with ascorbate, methylene blue, or superoxide dismutase attenuated the induction of function and expression for P-glycoprotein, suggesting that the reaction product between superoxide and NO is involved in the induction of function and expression. The level of nuclear translocation of nuclear factor-κB (NF-κB) and DNA binding activity of nuclear extracts to the NF-κB consensus oligonucleotide was increased in MBEC4 cells pretreated with SNP. Taken together, these observations suggest that nitrosative stress leads to the up-regulation of the message for the efflux transporter and, ultimately, to the enhanced function, probably via a NF-κB-dependent mechanism.

The purpose of this study was to examine the feasibility of applying a sample pooling method to the accelerated estimation of the uptake clearance of drugs to the brain in rats. Brain uptake clearances (CLuptake) were estimated for five model compounds using the sample pooling method and an integration plot analysis. CLuptakewas also evaluated for caffeine and theophylline by brain micro‐dialysis. The parameters and throughput of the pooling method were compared with those of typically used standard methods. The correlation for CLuptakewas statistically significant (P< 0.005) between the integration plot and the current method; the throughput of evaluation was 15‐fold higher for the sample pooling method. A comparison of CLuptakevalues indicated that the three methods showed comparable results for caffeine while the CLuptakeof theophylline using the proposed method was significantly different from those of the other methods. A kinetic analysis indicated that a compound with a slower CLuptakeand longer half‐life (e.g., theophylline) is more prone to error and that the lower limit of the CLuptakeof 0.17 mL min−1(g brain)−1may beset so as to have an error less than 20% of the estimation. These results suggest that the sample pooling method is applicable for use in the accelerated estimation of the uptake clearance of compounds in the brain for which the value is greater than 0.17 mL min−1(g brain)−1.

The purpose of this study was to examine the feasibility of applying a sample pooling method to the accelerated estimation of the uptake clearance of drugs to the brain in rats. Brain uptake clearances (CLuptake) were estimated for five model compounds using the sample pooling method and an integration plot analysis. CLuptakewas also evaluated for caffeine and theophylline by brain micro-dialysis. The parameters and throughput of the pooling method were compared with those of typically used standard methods. The correlation for CLuptakewas statistically significant (P< 0.005) between the integration plot and the current method; the throughput of evaluation was 15-fold higher for the sample pooling method. A comparison of CLuptakevalues indicated that the three methods showed comparable results for caffeine while the CLuptakeof theophylline using the proposed method was significantly different from those of the other methods. A kinetic analysis indicated that a compound with a slower CLuptakeand longer half-life (e.g., theophylline) is more prone to error and that the lower limit of the CLuptakeof 0.17 mL min−1(g brain)−1may beset so as to have an error less than 20% of the estimation. These results suggest that the sample pooling method is applicable for use in the accelerated estimation of the uptake clearance of compounds in the brain for which the value is greater than 0.17 mL min−1(g brain)−1.

The kinetics and mechanism by which tacrine is distributed in the rat brain were examined. Tacrine levels in plasma and striatal extracellular fluid were used to evaluate the pharmacokinetics of this process. The KD,brainwas decreased with the dose for tacrine, indicating that the distribution to the brain is saturable. The uptake of organic cations such as choline, 1-methyl-4-phenylpyridinium (MPP), tetraethylammonium (TEA), and carnitine was inhibited by the addition of tacrine to cultures of mouse immortalized brain capillary endothelial cells. In addition, the apical to basal transport and basal to apical transport of tacrine were inhibited by the addition of organic cations to cultures of LLC-PK1 cells, suggesting that tacrine transport across the blood-brain barrier (BBB) is mediated by organic cation transport system(s). Consistent with the in vitro results, a standard reverse transcription-polymerase chain reaction procedure was able to amplify the message of mOCT2 and mOCTN2, but not mOCT1, in MBEC4 (mouse brain microvessel endothelial cell line 4) cells. Similarly, mRNAs for rOCT2 and rOCTN2 were present in representative rat brain samples. To determine whether OCT2 and/or OCTN2 transport tacrine, these transporters were cloned and then transfected in SK-HEP1 and HEK 293 cells. The uptake of choline, MPP, and TEA was inhibited by the presence of tacrine in rOCT2-expressing SK-HEP1 cells, whereas the uptake of carnitine was inhibited by the presence of tacrine in rOCTN2-expressing HEK 293 cells. Collectively, these observations suggest that the transport of tacrine across the BBB is mediated, at least in part, by multiple organic cation transport systems in rats.

The kinetics and mechanism by which tacrine is distributed in the rat brain were examined. Tacrine levels in plasma and striatal extracellular fluid were used to evaluate the pharmacokinetics of this process. The KD,brain was decreased with the dose for tacrine, indicating that the distribution to the brain is saturable. The uptake of organic cations such as choline, 1-methyl-4-phenylpyridinium (MPP), tetraethylammonium (TEA), and carnitine was inhibited by the addition of tacrine to cultures of mouse immortalized brain capillary endothelial cells. In addition, the apical to basal transport and basal to apical transport of tacrine were inhibited by the addition of organic cations to cultures of LLC-PK1 cells, suggesting that tacrine transport across the blood-brain barrier (BBB) is mediated by organic cation transport system(s). Consistent with the in vitro results, a standard reverse transcription-polymerase chain reaction procedure was able to amplify the message of mOCT2 and mOCTN2, but not mOCT1, in MBEC4 (mouse brain microvessel endothelial cell line 4) cells. Similarly, mRNAs for rOCT2 and rOCTN2 were present in representative rat brain samples. To determine whether OCT2 and/or OCTN2 transport tacrine, these transporters were cloned and then transfected in SK-HEP1 and HEK 293 cells. The uptake of choline, MPP, and TEA was inhibited by the presence of tacrine in rOCT2-expressing SK-HEP1 cells, whereas the uptake of carnitine was inhibited by the presence of tacrine in rOCTN2-expressing HEK 293 cells. Collectively, these observations suggest that the transport of tacrine across the BBB is mediated, at least in part, by multiple organic cation transport systems in rats.

The in vivocanalicular excretion clearance of tributylmethyl ammonium (TBuMA), a P-glycoprotein (P-gp) substrate, was previously reported to be unaffected by the induction of an experimental hepatic injury (EHI) by CCl4despite the increased expression of P-gp in the EHI liver. The objective of this study, therefore, was to elucidate the mechanism for the unchanged canalicular excretion clearance of TBuMA in EHI rats. TBuMA uptake was increased in cLPM vesicles from EHI rats compared with that from control rats. The total bile salt concentration in EHI liver was significantly reduced compared with that in a control liver. Because, in our previous studies, the uptake of TBuMA by cLPM vesicles was found to be significantly enhanced in the presence of bile salts, the reduction in bile salt levels in the EHI liver may be related to the unaltered TBuMA clearance. Despite the fact that the uptake of TBuMA by cLPM vesicles was increased by the addition of an EHI liver extract, the extent of the increase was comparatively less compared to the addition of a control liver extract. The in vivoexcretion clearance of TBuMA was increased in a taurodeoxycholate dose-dependent manner in EHI rats. These observations suggest, therefore, that despite the induction of P-gp expression by the EHI, the in vivocanalicular excretion clearance of TBuMA remains unaltered as the result of an offset by reduced levels of bile salt(s).

The in vivo canalicular excretion clearance of tributylmethyl ammonium (TBuMA), a P‐glycoprotein (P‐gp) substrate, was previously reported to be unaffected by the induction of an experimental hepatic injury (EHI) by CCl4 despite the increased expression of P‐gp in the EHI liver. The objective of this study, therefore, was to elucidate the mechanism for the unchanged canalicular excretion clearance of TBuMA in EHI rats. TBuMA uptake was increased in cLPM vesicles from EHI rats compared with that from control rats. The total bile salt concentration in EHI liver was significantly reduced compared with that in a control liver. Because, in our previous studies, the uptake of TBuMA by cLPM vesicles was found to be significantly enhanced in the presence of bile salts, the reduction in bile salt levels in the EHI liver may be related to the unaltered TBuMA clearance. Despite the fact that the uptake of TBuMA by cLPM vesicles was increased by the addition of an EHI liver extract, the extent of the increase was comparatively less compared to the addition of a control liver extract. The in vivo excretion clearance of TBuMA was increased in a taurodeoxycholate dose‐dependent manner in EHI rats. These observations suggest, therefore, that despite the induction of P‐gp expression by the EHI, the in vivo canalicular excretion clearance of TBuMA remains unaltered as the result of an offset by reduced levels of bile salt(s). © 2004 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:317–326, 2005

The objective of this study was to examine the kinetics of the distribution of dehydroevodiamine (DHED) in the rat brain. After an intravenous infusion of 15min (dose of 1–10mg/kg), the temporal profiles of the plasma levels of DHED declined in a multiexponential manner. Moment analysis indicated that the clearance and steady‐state volume of distribution for DHED were not statistically different with the dose, indicating that the pharmacokinetics for DHED is linear in the range examined. Nonlinear regression analysis of DHED concentrations in the plasma and the brain revealed that the linear kinetics into and out from the brain reasonably described the data and that the clearances for influx into and efflux from the brain were comparable. Transport clearances for DHED across MBEC4 monolayers, an in vitromodel of the blood–brain barrier, were also comparable for influx and efflux, and were independent of the medium concentration. The concentration of DHED in cerebrospinal fluid was negligible compared with that found in plasma, indicating that the drug is not primarily distributed to the brain via the blood–cerebrospinal fluid barrier. These observations indicate that DHED is transported from the systemic circulation to the brain via the blood–brain barrier by linear kinetics. © 2004 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:283–292, 2004

The objective of this study was to examine the kinetics of the distribution of dehydroevodiamine (DHED) in the rat brain. After an intravenous infusion of 15 min (dose of 1–10 mg/kg), the temporal profiles of the plasma levels of DHED declined in a multiexponential manner. Moment analysis indicated that the clearance and steady-state volume of distribution for DHED were not statistically different with the dose, indicating that the pharmacokinetics for DHED is linear in the range examined. Nonlinear regression analysis of DHED concentrations in the plasma and the brain revealed that the linear kinetics into and out from the brain reasonably described the data and that the clearances for influx into and efflux from the brain were comparable. Transport clearances for DHED across MBEC4 monolayers, an in vitro model of the blood–brain barrier, were also comparable for influx and efflux, and were independent of the medium concentration. The concentration of DHED in cerebrospinal fluid was negligible compared with that found in plasma, indicating that the drug is not primarily distributed to the brain via the blood–cerebrospinal fluid barrier. These observations indicate that DHED is transported from the systemic circulation to the brain via the blood–brain barrier by linear kinetics. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:283–292, 2004

The effect of protein–calorie malnutrition (PCM) on the expression and functional activity of P-glycoprotein (P-gp) in the liver of rats was examined. Control protein diets and protein-restricted diets were fed to Sprague-Dawley rats for 4weeks, and the expression of P-gp in the liver (Western blot), in vitrouptake of a representative substrate of P-gp, daunomycin, into canalicular liver plasma membrane (cLPM) vesicles, and in vivocanalicular excretion of daunomycin were compared between the control and PCM rats. The expression of P-gp in the cLPM vesicles was decreased (22%, p<0.05) by PCM. Consistent with this result, the in vitrouptake rate (Vmax) was decreased (35%, p<0.05) by PCM, with constant affinity (Km), for the carrier-mediated uptake of daunomycin into cLPM vesicles, resulting in a 33% (p<0.05) decrease in the intrinsic uptake clearance (CLint). The in vivocanalicular excretion clearance (CLexc) of daunomycin was also decreased by 79% (p<0.01) in PCM rats, but the degree was more severe than would be expected from the 22% decrease in the expression of P-gp and the 33% decrease in the uptake of daunomycin (CLint). The hepatic level of adenosine 5′-triphosphate, which was decreased by 60% (p<0.01) in PCM rats, might have contributed to this severe decrease in CLexc. In summary, the canalicular excretion of P-gp substrates, such as daunomycin, might be reduced in patients with PCM via a mechanism involving the suppression of the expression of P-gp.

The effect of protein–calorie malnutrition (PCM) on the expression and functional activity of P-glycoprotein (P-gp) in the liver of rats was examined. Control protein diets and protein-restricted diets were fed to Sprague-Dawley rats for 4 weeks, and the expression of P-gp in the liver (Western blot), in vitro uptake of a representative substrate of P-gp, daunomycin, into canalicular liver plasma membrane (cLPM) vesicles, and in vivo canalicular excretion of daunomycin were compared between the control and PCM rats. The expression of P-gp in the cLPM vesicles was decreased (22%, p &lt; 0.05) by PCM. Consistent with this result, the in vitro uptake rate (Vmax) was decreased (35%, p &lt; 0.05) by PCM, with constant affinity (Km), for the carrier-mediated uptake of daunomycin into cLPM vesicles, resulting in a 33% (p &lt; 0.05) decrease in the intrinsic uptake clearance (CLint). The in vivo canalicular excretion clearance (CLexc) of daunomycin was also decreased by 79% (p &lt; 0.01) in PCM rats, but the degree was more severe than would be expected from the 22% decrease in the expression of P-gp and the 33% decrease in the uptake of daunomycin (CLint). The hepatic level of adenosine 5'-triphosphate, which was decreased by 60% (p &lt; 0.01) in PCM rats, might have contributed to this severe decrease in CLexc. In summary, the canalicular excretion of P-gp substrates, such as daunomycin, might be reduced in patients with PCM via a mechanism involving the suppression of the expression of P-gp. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1323–1330, 2003

Purpose.To examine the effect of ion-pair complexation with endogenous bile salts on the transport of organic cations (OCs) across LLC-PK1 cell monolayers. Methods.The transport of tributylmethyl-ammonium (TBuMA) and triethylmethylammonium (TEMA) across the cell monolayer was measured in the presence of taurodeoxycholate (TDC), an endogenous organic anion that forms an ion-pair complex with TBuMA, but not with TEMA. Results.Under proton gradient conditions (i.e., pH 6.0 apical/pH 7.4 basal), the above OCs exhibited similar transport charactersistics, consistent with the well-established OC/H+antiporter, and the presence of TDC had no measurable effect on the transport of these OCs. Under pH-equilibrated conditions (i.e., pH 7.4 apical/pH 7.4 basal); however, basal to apical transport of TBuMA, not that of TEMA, was increased in the presence of TDC, probably as a result of the formation of a lipophilic ion-pair complex between TBuMA and TDC. The transport and efflux of the TBuMA-TDC complex across the apical membrane of the cell was inhibited by representative substrates of the P-glycoprotein (P-gp), indicating the involvement of P-gp in this process. The increased affinity of the ion-pair complex to P-gp is consistent with a mechanism involving increased transport. Conclusion.In cases where there is no proton gradient between the plasma and urine, the formation of lipophilic ion-pair complexes in the kidney with endogenous bile salts might be involved in the in vivourinary excretion of large Mw OCs, such as TBuMA.

The objective of this study was to investigate the mechanisms by which berberine is transported in the secretory and absorptive directions across Caco-2 cell monolayers. The basolateral-to-apical (B-A) flux was 30-fold greater than the apical-to-basolateral flux and temperature dependent (i.e., drastic decrease at 4°C compared with 37°C). The above results suggest the involvement of a carrier-mediated active transport mechanism for the B-A transport of berberine. However, no significant concentration dependency for the permeability (Papp) of berberine was observed for B-A transport over a concentration range of 5–300 μM, indicating that the Kmvalue of berberine for the carrier system is greater than 300 μM. Well-documented P-glycoprotein (P-gp) substrates such as verapamil, daunomycin, and rhodamine123 inhibited the B-A flux of berberine, whereas tetraethylammonium and taurocholate did not, suggesting that P-gp is involved in the transport. For the case of daunomycin, the B-A flux, but not the apical-to-basolateral flux, was significantly increased after pretreatment of the cell monolayers with berberine. In addition, the uptake of 1 μM daunomycin into Caco-2 cells was decreased as a result of this pretreatment. These results suggest that the repeated administration of berberine may up-regulate P-gp functions in Caco-2 cells. If this occurs in the gastrointestinal epithelial cells, the repeated administration of berberine may reduce the gastrointestinal absorption of P-gp substrates including chemotherapeutic agents such as daunomycin. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association

The objective of this study was to investigate the mechanisms by which berberine is transported in the secretory and absorptive directions across Caco-2 cell monolayers. The basolateral-to-apical (B-A) flux was 30-fold greater than the apical-to-basolateral flux and temperature dependent (i.e., drastic decrease at 4°C compared with 37°C). The above results suggest the involvement of a carrier-mediated active transport mechanism for the B-A transport of berberine. However, no significant concentration dependency for the permeability (Papp) of berberine was observed for B-A transport over a concentration range of 5–300 μM, indicating that the Km value of berberine for the carrier system is greater than 300 μM. Well-documented P-glycoprotein (P-gp) substrates such as verapamil, daunomycin, and rhodamine123 inhibited the B-A flux of berberine, whereas tetraethylammonium and taurocholate did not, suggesting that P-gp is involved in the transport. For the case of daunomycin, the B-A flux, but not the apical-to-basolateral flux, was significantly increased after pretreatment of the cell monolayers with berberine. In addition, the uptake of 1 μM daunomycin into Caco-2 cells was decreased as a result of this pretreatment. These results suggest that the repeated administration of berberine may up-regulate P-gp functions in Caco-2 cells. If this occurs in the gastrointestinal epithelial cells, the repeated administration of berberine may reduce the gastrointestinal absorption of P-gp substrates including chemotherapeutic agents such as daunomycin. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2614–2621, 2002

The mechanism responsible for the reduced clearance of benzylpenicillin (BPC) from the cerebrospinal fluid (CSF) was investigated in rats that received an intracisternal administration of lipopolysaccharide (LPS). BPC was intraventricularly injected and its elimination from the CSF studied. During the inflammation created by the LPS administration to the cisterna magna, the clearance of BPC and taurine from the CSF was significantly reduced but reverted to the control level when N-nitro-l-arginine, a nitric oxide (NO) synthase inhibitor, was intracisternally administered. The in vitro uptake of BPC and taurine was significantly reduced in the choroid plexus (CP, the blood-CSF barrier) of rats with experimental inflammation and in control CP that had been pretreated with sodium nitroprusside (SNP, an NO donor). Interestingly, the clearance and CP uptake of formycin B, a substrate for a nucleoside transporter, were not affected by the experimental inflammation or by pretreatement with SNP. These observations suggest that the BPC transporter, and probably other transport systems as well, is functionally sensitive to NO in the blood-CSF barrier. Therefore, functional impairment of BPC transport in the CP by NO may be partly responsible for the increase in BPC concentration in the CSF during inflammation such as that caused by meningitis.

Purpose. The purpose of this study was to characterize the transport of uracil, a pyrimidine nucleobase, in Caco-2 and LLC-PK1cells. Methods. Caco-2 and LLC-PK1cells were grown to confluency on a permeable polycarbonate membrane insert to permit transport and uptake experiments after the loading of uracil on either the apical or basolateral side. Results. The vectorial transport of uracil in both directions was saturable with comparable Kmand Vmaxin Caco-2 cell monolayers, probably because of a Na+-independent transport system located on the basolateral membrane. In LLC-PK1cell monolayers, two distinct transport systems, namely a Na+-dependent and a Na+-independent, were functional in the apical to basolateral (A-B) transport of uracil. The first system was saturable with a Kmvalue of 3.67 ± 0.40 μM, a Vmaxof 11.31 ± 0.91 pmol/cm2/min, and a Na+:uracil coupling stoichiometry of 1.28 ± 0.20. The second system was Na+independent and satuable with a low affinity (Km, 50.37 ± 9.61 μM) and Vmax(16.01 ± 4.48 pmol/cm2/min). The two transport systems appeared to be located on the apical membrane. Conclusion. The mechanism of uracil transport differs depending on cell lines; a Na+-independent system on the basolateral membrane in Caco-2 cells and both Na+-dependent and Na+-independent systems on the apical membrane in LLC-PK1cells seem to be responsible for the difference.

The effect of pretreatment (i.e., oral administration of loxoprofen for 3 consecutive days followed by a 7-day washout) on the pharmacokinetics and metabolism of the drug was studied in humans. In a control study, a Loxonin® tablet (60mg as loxoprofen anhydrous) was administered orally to 6 healthy male Korean subjects. In a pretreatment study, a Loxonin® tablet was administered orally to the subjects once daily for 3 consecutive days. On the 10thday, a Loxonin® tablet was administered orally to the subjects, and the concentrations of loxoprofen and the trans- and cis-alcohol metabolites in the plasma and urine were measured as a function of time. Using this pretreatment, the area under the curve (AUC) of the trans-alcohol metabolite of loxoprofen in the plasma, but not those of loxoprofen and the cis-alcohol metabolite, was increased (1.5-fold, p<0.05), leading to increased contribution of the trans-alcohol metabolite to the total urinary recovery of loxoprofen (1.3-fold, p<0.05). The urinary recovery of total metabolites, which was largely (>90%) comprised of conjugate metabolites, was also increased as a result of the pretreatment (1.5-fold, p<0.05). These results indicate that stereoselective reduction to trans-alcohol metabolites as well as the phase II metabolism of loxoprofen may be increased by such a pretreatment in human subjects.

The effect of pretreatment (i.e., oral administration of loxoprofen for 3 consecutive days followed by a 7-day washout) on the pharmacokinetics and metabolism of the drug was studied in humans. In a control study, a Loxonin^® tablet (60 mg as loxoprofen anhydrous) was administered orally to 6 healthy male Korean subjects. In a pretreatment study, a Loxonin^® tablet was administered orally to the subjects once daily for 3 consecutive days. On the 10^th day, a Loxonin^® tablet was administered orally to the subjects, and the concentrations of loxoprofen and the trans- and cis-alcohol metabolites in the plasma and urine were measured as a function of time. Using this pretreatment, the area under the curve (AUC) of the trans-alcohol metabolite of loxoprofen in the plasma, but not those of loxoprofen and the cis-alcohol metabolite, was increased (1.5-fold, p &lt; 0.05), leading to increased contribution of the trans-alcohol metabolite to the total urinary recovery of loxoprofen (1.3-fold, p &lt; 0.05). The urinary recovery of total metabolites, which was largely (> 90%) comprised of conjugate metabolites, was also increased as a result of the pretreatment (1.5-fold, p &lt; 0.05). These results indicate that stereoselective reduction to trans-alcohol metabolites as well as the phase II metabolism of loxoprofen may be increased by such a pretreatment in human subjects. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:973–979, 2002

Protein-calorie malnutrition (PCM), as one of global health problems, arises during protein and/or energy deficit due to disease and nutritional inadequacy. Previously, we showed that PCM elicited oxidative stress with activation of the phase II detoxifying gene expression, which was reversed by cysteine supplementation. As part of the attempts to identify the cellular adaptive responses and the associated gene expression during PCM, the current study was initiated to analyze the genes differentially expressed in the rat during PCM. Among 1,916 bands amplified, 85 putative differentially amplified bands were enhanced by PCM in the liver, while the expression of 64 bands was suppressed. Northern and/or reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that PCM increased the expression of fibrinogen B β chain, B cell translocation gene 1 (BTG1) and thyroid hormone responsive protein (THRP) mRNAs. The increase in the hepatic fibrinogen B β chain mRNA was not prevented by cysteine supplementation, whereas cysteine decreased the enhancement in the rGSTA2 and microsomal epoxide hydrolase mRNA expression. Cysteine was also active in reversing the increase in BTG1 mRNA during PCM. This was supported by the increase in BTG1 mRNA in H4IIE cells exposed to sulfur amino acid-deprived medium. Northern blot analysis revealed that THRP, highly expressed in the brain in a tissue-specific manner, was induced by PCM and that cysteine supplementation abolished the THRP induction. Conversely, the level of hepatic albumin mRNA was markedly decreased by PCM, which was partially restored by cysteine supplementation. Differential display RT-PCR analysis allowed us to identify the genes that are responsive to oxidative stress during PCM and to characterize the differential role of cysteine on the expression of the fibrinogen B β chain, BTG1 and THRP genes as a homeostatic adaptive response during protein deficiency.

A simple liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the quantification of salmon calcitonin (sCT) in serum. Serum samples from rats and dogs were deproteinized and freeze-dried. The residue was then reconstituted with 57% acetonitrile in water containing 0.1% trifluoroacetic acid and 0.005% benzalkonium chloride. A 20-μl aliquot of the reconstituted solution was injected onto a polymer based RP-C 18 column, The outlet was connected to an ion-trap mass spectrometer equipped with an ESI source, and spectra were recorded in a positive-ion, selected-ion monitoring mode. The limit of quantification of the method was 10 ng/ml. Biexponential curves were observed for the temporal serum concentration of sCT following intravenous administration of sCT to rats (100 μg/kg) and dogs (250 μg/kg), resulting in reasonable pharmacokinetic parameters. The present method appears applicable to routine analysis of serum sCT in pharmacokinetic studies with good selectivity, accuracy and precision.

5,6-Dimethyl-2-(4-fluorophenylamino)-4-(1-methyl-1,2,3,4-tetrahydroisoquinoline-2-yl) pyrimidine hydrochloride (YH1885) is under development as a novel acid pump antagonist by Yuhan Research Center. Previous studies have suggested that the AUC and Cmaxof orally dosed YH1885 are dose-dependent in the range of 2 to 500 mg/kg. The objective of the present study was to investigate the absorption mechanism of YH1885 using a human colon carcinoma cell line, Caco-2. The cells were grown to confluency on a permeable polycarbonate membrane insert to permit loading of YH1885 on either the apical or basolateral side of the cell monolayer. The flux across the monolayer from the apical to basolateral side was 3 to 5 times greater than that from the basolateral to apical side. The uptake of YH1885 into the Caco-2 cell monolayer was saturable and appeared to be mediated by a high-affinity transporter, with an apparent Kmof 1.47 ± 0.21 μM and a Vmaxof 25.14 ± 1.16 pmol/cm2/40 s. The apical to basolateral transport across the monolayer was Na+-independent, H+-sensitive, and energy-dependent. The transport was inhibited significantly by the presence of structural analogs of YH1885 (e.g., YH957, YH1070, and YH1041), some pyrimidine nucleobases (uracil and 5-methyluracil), and nucleobase transport inhibitors (e.g., papaverine, dipyridamole, and phloridzin). These results demonstrate that the apical to basolateral transport of YH1885 across the Caco-2 cell monolayer is partially mediated by a nucleobase transport system, which exhibits high-affinity and energy-dependent properties for YH1885. Saturation of this transport system, in addition to the limited solubility of YH1885 (i.e., ∼5.3 μM), appears to contribute to the dose-dependent bioavailability of the drug.

Purpose.The effect of CCl4-induced experimental hepatic failure(EHF) on the sequential hepatobiliary transport of model organiccations (OCs), triethylmethylammonium (TEMA), and tributylmethylammonium (TBuMA), was investigated in rats. Methods.EHF was induced by an i.p. injection of CCl4at a dose of1 ml/kg 24 hr prior to the transport study. The cumulative in vivobiliary excretion, in vitrohepatic uptake by isolated hepatocytes,in vitroefflux (i.e., release) from hepatocytes, andin vivohepatobiliary excretion clearance were measured for normal and CCl4-EHF rats. Results.The CCl4-EHF decreased the apparentin vivobiliary clearance (CLo) and the in vitromaximum uptake rate (Vmax, uptake) of TBuMA by 66 and 48%,respectively. The CCl4-EHF had no effect on the CLoof TEMA, but decreased both the Vmax, uptake(59%) and thein vitromaximum hepatic efflux rate (Vmax, efflux) of TEMA (80%). On thecontrary, the CCl4-EHF had no influence on the in vivohepatobiliaryexcretion clearance (CLexc) of both OCs. Conclusions.Transport systems for the OCs on the sinusoidal membrane(uptake and/or efflux), rather than those on the bile canalicularmembrane (excretion) appear to be prone to damage by the CCl4-EHF.

Two structurally similar quaternary ammonium compounds, triethylmethylammonium (TEMA, Mr116) and tributylmethylammonium (TBuMA, Mr200) were used as model compounds to identify the unit process of hepatobiliary excretion that is responsible for markedly different biliary excretion of organic cations (OCs). Cumulative biliary excretion (in percentage of dose; i.v., 12 μmol/kg) was 0.17 for TEMA and 34.5 for TBuMA. In vivo uptake clearance into the liver was 0.686 ± 0.020 ml/min for TEMA and 0.421 ± 0.028 ml/min for TBuMA. When the uptake clearance was examined in an isolated hepatocyte system, comparable clearance between TEMA and TBuMA was obtained, consistent with the in vivo result. These observations suggest that uptake into the liver is not the major determinant for the difference in biliary excretion of the OCs. Coadministration of colchicine, an inhibitor of microtubule formation, had no effect on biliary excretion of the model compounds, and the primary site of subcellular distribution of the OCs appears to be the cytosol, suggesting that intracellular movement does not play a major role in the markedly different biliary excretion of the OCs. In contrast, in vivo excretion clearance across the canalicular membrane for TBuMA was 180-fold greater than that for TEMA, and in vitro efflux clearance of TBuMA was smaller than that of TEMA (p< .01), indicative of involvement of these processes in the markedly different biliary excretion of the OCs. Therefore, these data indicate that canalicular transport is primarily responsible for the markedly different biliary excretion of TEMA and TBuMA.

Purpose. The mechanism(s) responsible for the significantly higher biliary excretion of tributyl methyl ammonium (TBuMA) than of tri-ethyl methyl ammonium (TEMA) was investigated in canalicular liver plasma membrane vesicles (cLPM). Methods. The uptake of [3H]TBuMA and [3H]TEMA into cLPM in the presence of a pH gradient or ATP was measured by a rapid filtration technique. Results. The uptake of substrates into the vesicle was significantly increased by an outwardly directed pH gradient. The pH dependent uptake was saturable and cross-inhibited by the other organic cation, indicating that TEMA and TBuMA share a common transport mechanism. Kinetic analysis revealed the two compounds show similar characteristics for the pH-gradient dependent uptake. Thus, the organic cation/H+exchange mechanism does not appear to explain the significant difference in biliary excretion of the organic cations. In the presence of ATP, however, uptake into cLPM was readily observed for TBuMA while TEMA uptake was negligible. Inhibition studies with typical P-glycoprotein substrates indicated the uptake may be mediated by the P-glycoprotein. Conclusions. Differences between TBuMA and TEMA in reactivity for an ATP dependent transport process, rather than for an organic cation/H+exchanger, may be responsible for the markedly different biliary excretion of TBuMA and TEMA.

The effect of uranyl nitrate (UN)-induced acute renal failure (ARF) on the pharmacokinetics of diltiazem (DTZ) was examined in rats through in vitro and in vivo studies. In vitro homogenate studies demonstrated that DTZ was metabolized to deacetyl diltiazem (DAD) predominantly in the liver. Metabolism in the small intestine, kidney, or blood pool was negligible compared with that in the liver. UN-induced ARF (UN-ARF) increased the in vitro hepatic clearance (CLvit) of DTZ 1.4-fold. In vivo pharmacokinetic studies following intravenous (iv) and portal venous (pv) administration revealed that UN-ARF increased the intrinsic clearance (CLi) of DTZ from 243.0 to 414.5 ml/min/kg but decreased its total plasma clearance (CLt) from 90.3 to 64.3 ml/min/kg. The increase in CLi was consistent with the increase in CLvit of the liver. The in vitro plasma free fraction of DTZ (fp) was decreased from 0.25 to 0.14 by UN-ARF, but the in vitro blood/plasma partition of DTZ (Rb) remained constant at unity. From the CLi and fp changes, the plasma intrinsic clearance for unbound DTZ (CLi') was calculated to be increased 2.7-fold, from 1104.5 to 2960.7 ml/min/kg, by UN-ARF. The fp decrease was also reflected in the steady-state distribution volume (Vdss) of DTZ, which was decreased significantly from 3595.5 to 2528.3 ml/kg. The absolute bioavailability of pv DTZ (Fpv) was decreased by UN-ARF from 37.5 to 15.5% but was still much higher than the reported oral bioavailability (6%), indicating poor absorption of DTZ from the GI tract. From the calculation based on a well-stirred pharmacokinetic model, DTZ was found to increase the hepatic blood flow (HBF) of the control rats more than twofold at doses of 3 mg/kg (iv) or 10 mg/kg (pv), possibly due to the vasodilating effect of DTZ. However, the effect of DTZ on HBF was not present in the UN-ARF rats. It is not clear at present whether this could be attributed to vasoconstricting effects of UN-ARF or blockade of the vasodilating effect of DTZ.

Aucubin, a promising hepatoprotecting iridoid glucoside, was given intravenously (iv), orally (po), intraperitoneally (ip), and hepatoportally (pv) to rats. A linear pharmacokinetic behavior was obtained after iv administration of 40–400 mg/kg of aucubin. The half-life of aucubin in the postdistributive phase (t1/2,ß), total-body plasma clearance (CLt), and volume of distribution (Vdss) were 42.5 min, 7.2 ml/min/kg, and 346.9 ml/kg, respectively, for a 40 mg/kg dose. There was no significant difference in the parameters as a result of increasing dose. The partition coefficients of aucubin between n-octanol and buffers of pH 3.0–10.0 were low, while 18.5 ± 1.3% of aucubin in whole blood partitioned into the blood cells. Plasma protein binding of aucubin was only 9%. The bioavailabilities of aucubin after administration at a dose of 100 mg/kg through pv, ip, and po routes were 83.5, 76.8, and 19.3%, respectively. The pH-stability profile indicated rapid degradation of aucubin at pH 1.2, 1.6, and 2.0, with degradation half-lives of 5.1, 5.8, and 14.8 hr, respectively, at 37°C. Therefore, the low oral bioavailability of aucubin may be attributed to pH-instability in the gastric fluid, poor GI absorption due to low lipophilicity, and the possible metabolism in the GI mucosa and liver (so called first-pass effect).

Inter- and intrasubject variations of ranitidine pharmacokinetics were examined following oral administration of ranitidine tablets (150mg as base) under controlled conditions at a timed interval of one week (periods I and II) to 12 healthy male subjects. Significant secondary peaks in the plasma concentration-time curves were observed in all subjects in both periods. The first peak occurred at 0.5 to 2.5h and the second peak at 3 to 6h after the dosing. There were great variations in the plasma concentration–time profiles among subjects; for example, the area under the plasma concentration–time curve from time 0 to 12h (AUC0–12) varied from 1905 to 5672 μg-h/mL. But bioavailability parameters of period I, such as maximum concentration of the first and second plasma peak (Cmax 1, and Cmax 2, respectively), time to first peak (tmax 1), AUC0–12, and AUC from time zero to infinity (AUC0–∞), were correlated significantly with those of period II. These results suggest that the intrasubject variation of ranitidine pharmacokinetics is usually small over at least one week under the controlled conditions of this study, in spite of its great intersubject variation.

The objectives of this study were to characterize the pharmacokinetics of 1-5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-1-piperazinyl)-1,4-dihydro-4-oxoquinolone-3-carboxylic acid hydrochloride (DW-116), a newly developed quinolone antibiotic, and to compare these kinetics with those of ciprofloxacin and rufloxacin, representative quinolone antibiotics, in rats. Rats were subjected to surgery involving catheterization of the femoral vein and artery. DW-116 (4, 20, or 200 mg/kg), ciprofloxacin (20 mg/kg), or rufloxacin (20 mg/kg) was administered either intravenously (iv) or orally. Blood samples were collected at various times and subjected to an HPLC assay for the quinolones. Temporal profiles of plasma concentration after iv administrations of DW-116 at doses of 4, 20, and 200 mg/kg exhibited an apparent multiexponential decline. In the three doses examined, systemic clearance and steady-state volume of distribution of DW-116, calculated by model-independent methods, were in the range 0.17~0.23 L/h/kg and 2.90~4.44 L/kg, respectively. When DW-116 was given orally at doses of 4, 20, or 200 mg/kg, the AUC values were nearly identical to those following iv administration, indicating an almost complete absorption (i.e., the percent bioavailability was 90.0 for 4 mg/kg, 99.0 for 20 mg/kg, and 98.3 for 200 mg/kg) in the dose range examined. The absorption of DW-116 appears to be extremely rapid because the mean residence time calculated from the oral administration data was not significantly different from that for the iv administration. At a dose of 20 mg/kg, the mean residence time for iv administered ciprofloxacin and rufloxacin was smaller than that of DW-116, indicating that DW-116 remains in the body longer than the other quinolones. Absolute percent bioavailabilities of ciprofloxacin (69.9%) and rufloxacin (84.9%) were smaller than that obtained for DW-116 (99.0%). Because it has been reported that the in vivo antibacterial activity of DW-116 is comparable or superior to that of rufloxacin and ciprofloxacin, despite the fact that the in vitro activity is significantly lower, the pharmacokinetics of this antibiotic may be responsible, at least in part, for the enhanced in vivo antibacterial activity of DW-116.

Nasal absorption of sulfobromophthalein (BSP) and amaranth (AM) was investigated and compared with oral absorption in the rat. Bioavailability of BSP and AM after nasal administration was about 26% and 30% respectively. Oral absorption of them was not detected. Nasal route was considered more effective than oral route for these anionic model drugs, but their nasal bioavailability was not so good as expected from the reports for other drugs. High nasal mucus binding of BSP and AM were implied by their high binding to plasma protein (97% and 94%) or to intestinal mucus (78% and 81%). They seemed to have very low lipophilicity since their apparent partition coefficient(APC) between phosphate buffer of various pH and n-octanol were almost zero. They have too large molecular size to pass through the pore (<0.4nm) of nasal mucus membrane. Therefore it was concluded that the low nasal bioavailability of these anionic model drugs might be due to either nonspecific binding to nasal mucus, or low lipophilicity to pass the nasal mucus membrane, or their large molecular size to pass through the pore route of the nasal mucus. Possibility of nasal metabolism in the mucus membrane was excluded since the reported enzymes in the nasal mucus may not affect the metabolism of them.

Correlation between in vitro dissolution characteristics and in vivo salivary bioavailability parameters of four commercial sustainedrelease and one immediate-release theophylline (TP) or aminophylline dosage forms were examined. Area under the saliva concentration-time curve up to 6h (AUC0→6), peak saliva concentration (Cmax), and fraction absorbed in 1h (F1), based on saliva concentration following oral administration of TP or aminophylline dosage forms to five volunteers, were closely correlated with percents dissolved in pH 6.8 buffer in 30 min, D30 (6.8), or 60 min, D60 (6.8). Dissolution study in pH 6.8 buffer seemed to be a useful tool for development, evaluation, and quality control of sustained-release dosage forms of TP, since the saliva concentration was reported to represent the blood concentration of TP indirectly.

Proliposomes were prepared by the penetration of a methanol-chloroform solution of propranolol hydrochloride (PH) and lecithin into microporous sorbitol, with subsequent vacuum drying. They were characterized for surface morphology and flowability, and following the conversion to liposomes upon hydration, size distribution, drug content and in vitro drug release of the reconstituted liposomes were examined. The porous structure of sorbitol was maintained in the proliposomes, affording the proliposomes good flowability at lecithin-to-sorbitol ratios (w/w) of not more than 0.2. Multilamellar liposomes were reconstituted spontaneously from the proliposomes upon hydration. The mean diameter of the resultant liposomes was highly dependent on the PH-to-lecithin ratio, but less dependent on the lecithin-to-sorbitol ratio and sorbitol particle size (105-710μm). Entrapment efficiency of PH in liposomes showed a maximum 10% at PH-to-lecithin ratio <0.5 and a lecithin-to-sorbitol ratio < 0.1. Sustained release of propranolol from the proliposomes was achieved when the lecithin-to-PH ratio was < 2, and the lecithin-to-sorbitol ratio was in the range examined (0.06742). In conclusion, granular proliposomes of PH with good flowability and sustained release characteristics could be prepared by controlling the drug/lecithin/sorbitol ratio and sorbitol particle size. PH proliposomes can be potential candidates for the sustained drug delivery of propranolol when applied directly onto the mucosal membranes.

Administration route dependent bioavailability of recombinant human interferon alpha (IFN-α) and effect of seven bile salts and polyoxyethylene-9-lauryl ether (BL-9) on nasal absorption of IFN-a were studied in rats. IFN-a (1.5 × 10 7 IU/kg) was administered through iv, pv, po and ip routes and AUC of the routes were compared. As a result, it was found that IFN-α is extracted almost completely during its passage through the GI lumen, and is not absorbed from the GI lumen. Moreover, IFN-α sparingly transported through the GI lumen suffers additional extraction by the GI mucosa (57%) and the liver (8%) consecutively and only about 40% of it can reach the systemic circulation. Therefore, a high bioavailability of IFN-a cannot be expected through the oral route even with the aid of absorption enhancers. On the other hand, significant absorption of IFN-α could be attained through the nasal route with some absorption enhancers (1% w/v). Among the enhancers examined, sodium cholate (CH), sodium glycocholate (GC), sodium taurocholate (TC), sodium glycodeoxycholate (GDC), sodium taurodeoxycholate (TDC) and BL-9 increased the nasal bioavailability of IFN-a. However, sodium dehydrocholate (DHC) and sodium deoxycholate (DOC) did not show such effect. Nasal bioavailability of IFN-a was increased up to 32.3 (± 15.5)% by 1% TC. The enhancing effect of TC was significantly (p<0.05) greater than those of CH, DOC, DHC and BL-9. TC and GC seemed to be potential candidates for the nasal absorption enhancers of IFN-α, considering that they are reportedly less toxic than GDC and TDC.

The effect of cimetidine (CM) on the pharmacokinetics of fentiazac (FT) was studied in six rats. FT was administered by intravenous (iv) bolus injection at doses of 5, 10, and 20 mg/kg to rats receiving iv infusion of saline (control) or CM. The infusion of CM was conducted to achieve steady-state plasma concentrations (Css) of CM of 30 and 60 μg/mL. In the control rats, the plasma disposition of FT and its major metabolite, p-hydroxy FT, followed a classical drug-metabolite profile irrespective of FT dose. The plasma level of p-hydroxy FT was comparable with that of FT. The disappearance of FT from the rat plasma was significantly delayed by the CM infusion, and p-hydroxy FT was undetectable in the plasma in CM-treated rats. The total body clearance (CLtof FT was decreased to 20–50% of the control value in CM-treated rats, implying that FT metabolism to p-hydroxy FT is almost completely impaired by CM. The CLtvalues in rats with different Cssof CM (30 and 60 μg/mL) were not significantly different from each other. The distribution volume of FT at steady state (Vdss) was decreased to 60–70% of the control value by the CM infusion at higher doses of FT (10 and 20 mg/kg). The decreases in Vdssand CLtseem not to be related to the binding of FT to plasma protein because the binding of FT was not influenced by CM. In clinical settings, the magnitude of the pharmacokinetic difference may warrant dose adjustment to avoid toxic effects of FT when administered with CM.

The objectives of this study were to characterize the pharmacokinetics of 1-5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-1-piperazinyl)-1,4-dihydro-4-oxoquinolone-3-carboxylic acid hydrochloride (DW-116), a newly developed quinolone antibiotic, and to compare these kinetics with those of ciprofloxacin and rufloxacin, representative quinolone antibiotics, in rats. Rats were subjected to surgery involving catheterization of the femoral vein and artery. DW-116 (4, 20, or 200mg/kg), ciprofloxacin (20mg/kg), or rufloxacin (20mg/kg) was administered either intravenously (iv) or orally. Blood samples were collected at various times and subjected to an HPLC assay for the quinolones. Temporal profiles of plasma concentration after iv administrations of DW-116 at doses of 4, 20, and 200mg/kg exhibited an apparent multiexponential decline. In the three doses examined, systemic clearance and steady-state volume of distribution of DW-116, calculated by model-independent methods, were in the range 0.17∼0.23L/h/kg and 2.90∼4.44L/kg, respectively. When DW-116 was given orally at doses of 4, 20, or 200mg/kg, the AUC values were nearly identical to those following iv administration, indicating an almost complete absorption (i.e., the percent bioavailability was 90.0 for 4mg/kg, 99.0 for 20mg/kg, and 98.3 for 200mg/kg) in the dose range examined. The absorption of DW-116 appears to be extremely rapid because the mean residence time calculated from the oral administration data was not significantly different from that for the iv administration. At a dose of 20mg/kg, the mean residence time for iv administered ciprofloxacin and rufloxacin was smaller than that of DW-116, indicating that DW-116 remains in the body longer than the other quinolones. Absolute percent bioavailabilities of ciprofloxacin (69.9%) and rufloxacin (84.9%) were smaller than that obtained for DW-116 (99.0%). Because it has been reported that the in vivoantibacterial activity of DW-116 is comparable or superior to that of rufloxacin and ciprofloxacin, despite the fact that the in vitroactivity is significantly lower, the pharmacokinetics of this antibiotic may be responsible, at least in part, for the enhanced in vivoantibacterial activity of DW-116.

Multiple plasma peaks of acetaminophen (AAP) were observed following oral administration of an AAP (40 mg/kg) suspension to fasted rats. The multiple peaks were not diminished when the AAP suspension was administered to enterohepatic recycling-blocked (ERB) rats. Therefore, enterohepatic recycling does not contribute significantly to the multiple peaks of orally administered AAP in rats. After intravenous administration of AAP (40 mg/kg) solution to 10 rats, 10% of the rats showed distinct multiple plasma peaks. This indicates that multiple peaks may be unrelated to the gastrointestinal absorption process for some drugs.

ABSTRACTDimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB) has been shown to improve liver function in chronic hepatitis patients. Despite the fact that the oral bioavailability for DDB appears to be low and variable, the intestinal absorption of the drug is not well understood because of the lack of sensitivity and inadequate separation of DDB from endogenous peaks derived from the serum in previously developed HPLC assays. The present study describes a reliable HPLC method for DDB in serum samples for normal dose human bioavailability trials. A deproteinated serum sample was subjected to a solid-phase extraction procedure. The residue of the Sep-Pak eluent was reconstituted in acetonitrile and an aliquot was directly injected onto an octadecyl silica column (4 μm, 250 x 4.5mm I.D.). The mobile phase consisting of acetonitrile and water (52.5% acetonitrile in water, v/v), was delivered at a flow rate of lml/min, and DDB elution from the HPLC column was monitored by UV absorption at 278nm. The assay was linear in the range of 5-100ng DDB/ml serum with inter-day and intra-day variation less than 14.3 and 13.2 %, respectively. To determine whether the HPLC assay can be utilized in normal dose bioavailability studies, human serum samples (1ml each) were obtained from a typical normal dose bioavailability study (oral capsule for DDB; 15 mg as DDB) and analyzed for DDB. The drug was readily detectable in all samples from 30min to 720min after administration. Therefore, these data indicate that this HPLC assay is readily applicable to a normal dose pharmacokinetic study of DDB in human subjects.

The in-viva cutaneous absorption of hydrocortisone was examined following topical application of hydrocortisone-containing liposomes. The formulation was applied onto the skin (1.0cm2) of the hairless mouse (at a dose of 0.1 mg hydrocortisone) in the presence and absence of occlusion, and temporal profiles of the drug in the skin (stratum corneum and viable skin) were monitored. Under the non-occluded condition, the drug amount in the stratum corneum and viable skin reached its maximuim within 1 h, and then decreased rapidly. Gelation of the liposomes by complete dehydration of the formulation under non-occlusion, which may prevent partition of the drug into the skin, appears to be a cause of the rapid decrease. Under the occluded condition, the drug amount in the skin was sustained although it then decreased dramatically compared with that under the non-occlusion (i.e. approximately 1/22 for stratum corneum and 1/8 for viable skin at 1 h, for example). A prevention of gelation of the liposomes by occlusion appears to be a potential mechanism of the maintenance of the drug concentration in the skin. The dramatic decrease in drug content in the skin may be attributed to the reduced partition of hydrocortisone, a hydrophobic drug, from the liposomes into the hydration-maintained stratum corneum under occlusion. In both application conditions, the concentration of hydrolcortisone in the hydrophilic viable skin layer was markedly lower than that in the stratum corneum, indicating that partitioning between these tissues is a primary determinant of hydrocortisone reaching viable skin tissue. The estimated penetration depth of the drug into the stratum corneum was not affected significantly by the application conditions. These results demonstrate that excessive dehydration (non-occlusion) is not desirable for the prolonged delivery of hydrocortisone from liposomes into the skin. They also indicate the either hydration of the dosed skin (occlusion) is not preferable for the efficient delivery of hydrocortisone from the liposomes to the skin, especially to the viable skin. Therefore, both excessive dehydration of the liposomes and excessive hydration of the dosed skin (occlusion) should be avoided in the topical application of liposornal formulations for efficient delivery of hydrocortisone to the skin for a prolonged period of time.

AimsThe objective of this study was to determine the extent of period effect on the pharmacokinetics of cyclosporin A (CsA) during consecutive dosing.

Aims The objective of this study was to determine the extent of period effect on the pharmacokinetics of cyclosporin A (CsA) during consecutive dosing.

The oral absorption of omeprazole is incomplete, in part due to first-pass metabolism. We investigated the feasibility of rectal administration of omeprazole by comparing its absorption from a Witepsol H15-based rectal suppository and an orally administered commercial gelatin capsule in 10 male volunteers. Profiles of plasma concentration between two preparations (20mg) were not statistically different, indicating that the rate and the extent of absorption were similar. Paired t-test revealed no significant differences in area under the curve, mean residence time, and time to peak concentration between two preparations. On the other hand, lag time of absorption and peak concentration were statistically different (p<0.05) between these preparations. Under these experimental conditions, the rectal route did not produce an improvement in the extent of absorption over an oral capsule.

We demonstrated that an aqueous extract of dried immature fruit of Poncirus trifoliate(PF-W) produces relaxation of intestinal smooth muscle using the ileac strips of a rat. Furthermore, the underlying mechanism of its relaxant activity was investigated. PF-W was prepared using the standard extraction protocol. A 1.5 – 2 cm long rat ileac strip was placed in an organ bath with Tyrode's solution and smooth muscle contractility was recorded by connecting it to a force transducer. Various compounds were added to the organ baths, and changes in muscular contractility were measured. PF-W concentration-dependently induced relaxation of rat ileac strips that were contracted both spontaneously and via acetylcholine treatment. Various potassium channel blockers did not inhibit the relaxation by PF-W. No difference in the effect of PF-W was observed between ileac strips treated with low (20 mM) and high concentrations (60 mM) of KCl. PF-W inhibited the contraction of rat ileac strips induced by extracellular calcium. PF-W acts as a potent smooth muscle relaxant, implicating its possible action as a rapid acting reliever for abdominal pains and a cure for intestinal convulsion. Considering that PF-W also exhibits prokinetic activity, its use in various gastrointestinal disorders seems promising.