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This study was designed to investigate the impact of cytochrome P450 ( CYP) 1 A2 polymorphisms on theophylline metabolism in a non-smoking healthy male Chinese population. Four polymorphisms CYP1 A2*1 C ( G-3860 A), G-3113 A, CYP1 A2*1 F ( C-163 A) and CYP1 A2*1 B ( C-5347 T) were screened in 238 unrelated male volunteers. Then, a single oral 200-mg dose of theophylline was administered to 37 volunteers, who were selected from 238 volunteers based on the CYP1 A2 genotype. CYP1 A2 activities were evaluated by plasma 1,7-dimethylxanthine/caffeine ratios (17 X/137 X) after administration of 100-mg caffeine. The plasma concentrations of theophylline, 17 X and 137 X were determined by high-performance liquid chromatography. The activity of CYP1 A2 was lower in volunteers with the -3113 AA genotype compared with those with the -3113 AG genotype (0.35 ± 0.04 versus 0.48 ± 0.07, p = 0.016) or the -3113 GG genotype (0.35 ± 0.04 versus 0.58 ± 0.22, p = 0.037). CYP1 A2*1 F polymorphisms were associated with increased CYP1 A2 activity in volunteers with -3860 G/-3113 G/5347 C homozygosity (0.66 ± 0.24 versus 0.46 ± 0.05, p = 0.034). However, theophylline metabolism showed no difference among volunteers carrying different haplotype pairs. CYP1 A2 genetic polymorphisms influenced CYP1 A2 enzyme activity as measured by caffeine, but CYP1 A2 gene polymorphisms appeared to have limited influence on theophylline metabolism in our study. [ABSTRACT FROM AUTHOR]

Objective: To determine the pharmacokinetic interaction between cefaclor and bromhexine in healthy Chinese volunteers., Methods: Twelve subjects received a cefaclor (CEF) treatment, a bromhexine (BHX) treatment, and a co-treatment of CEF and BHX with a 3 x 3 Latin square design. The wash-out time between periods was 14 days. The plasma and urine drug concentrations of CEF and BHX were detected by HPLC-UV and LC/MS, respectively., Results: All the 12 volunteers completed the study. There were no significant differences in AUC 0-t and Cmax of CEF in logarithm between the single administration group of CEF and the co-administration group of CEF with BHX. Two one sided t-test showed that CEF was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, and Clr between the 2 groups. Vd/F was significantly lower in the single CEF group than in the co-administration group of CEF and BHX. There were no significant differences of AUC 0-t and Cmax of BHX in logarithm between the single administration group of BHX and the co-administration group of BHX with CEF. Two one sided t-test showed that BHX was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, Vd/F, and Clr between the 2 groups., Conclusion: There is no significant pharmacokinetic parameter change in the drug absorption, metabolism, and excretion, but Vd/F of CEF significant increases in the co-administration of CEF with BHX. The co-administration of CEF and BHX has no adverse drug interaction. The increase of Vd/F may be a favorable drug interaction, which may be the mechanism of the synergistic effect of the 2 drugs.

Objective: To explore the inhibitive effects of 1,3,8-trihydroxy-5-methoxyxanthone (TMX) on cytochrome P450s (CYP450s) in human liver microsomes., Methods: Probe drugs were incubated with and without adding TMX to determine the changes of enzyme activities. The concentration ratio of metabolites to probe drugs was used to present enzyme activities. Concentrations of the probe drugs and their metabolites in the incubated mixture were detected by high performance liquid chromatography., Results: The variations (mean, 95%CI) of the activities of CYP1A2, CYP2C9, CYP2C19, CYP2E1 and CYP3A4 were 2.95 x 10(-3) (2.03 x 10(-3), 3.88 x 10(-3)), 3.14 x 10(-2) (1.87 x 10(-2), 4.42 x 10(-2)), 2.27 x 10(-3) (-1.4 x 10(-2),1.81 x 10(-2)), 7.72 x 10(-2) (-0.83 x 10(-2), 0.2374), and -0.2548 (-2.9802, 2.4707), respectively. The activities of CYP1A2 and CYP2C9 were significantly reduced in the present of TMX., Conclusion: TMX (10 micromol/L) has significant inhibitive effect on the activities of CYP1A2 and CYP2C9, but no significant inhibitive effect on the activities of CYP2C19, CYP2E1 and CYP3A4.

Objective: To determine the pharmacokinetics of erythromycin stinoprate capsules and to provide guidance for clinical research., Methods: Thirty healthy volunteers (15 men and 15 women) were divided into 3 groups randomly, each including 5 men and 5 women. Single oral doses of 250, 500 and 750 mg were given to each volunteer. The concentrations of erythromycin propionate and erythromycin base in the plasma were determined by HPLC-MS., Results: All 30 volunteers completed the experiment without adverse reactions. Using 3P87 we analyzed the model and calculated the pharmacokinetic parameters. Three dose groups taking high, middle and low dose were all single compartment model. The pharmacokinetic parameters of erythromycin propionate after taking erythromycin stinoprate capsules were as follows: Low dose group: Ka (2.007 +/- 1.281 )/h, tmax ( actual value) (1.9 +/- 0.6) h, Cmax (437.0 +/- 295.0) microg/L, AUC0-14 (trapezoid area) (1840.2 +/- 1476.87) microg x h/L, Ke (0.329 +/- 0.119)/h, T1/2 (2.45 +/- 0.9) h. Middle dose group: Ka (1.451 +/- 0.380)/h, tmax (1.7 +/- 0.3) h, Cmax (923.1 +/- 217.5) microg/L, AUC0-14 (4542.44 +/- 1579.4) microg x h/L,Ke (0.237 +/- 0.057)/h, T1/2 (3.1 +/- 1.1) h; High dose group: Ka (2.076 +/- 1.559)/h, tmax (1.7 +/- 0.3) h, Cmax (1336.5 +/- 366.0) microg/L, AUC0-14 (7481.5 +/- 2496.2) microg x h/L, Ke (0.266 +/- 0.051)/h, T1/2 (2.7 +/- 0.5) h. The pharmacokinetic parameters of erythromycin were as follows: Low dose group: Ka (1.410 +/- 0.626)/h, tmax (1.8 +/- 0.5) h, Cmax (197.5 +/- 227.6) microLg/L, AUC0-14 (766.4 +/- 981.0) microg x h/L, Ke (0.519 +/- 0.240)/ h, T1/2 (1.6 +/- 0.8) h. Middle dose group: Ka (1.900 +/- 1.049)/h, tmax (1.6 +/- 0.2) h,Cmax (488.3 +/- 216.7) microg/L, AUC0-14( 488.3 +/- 216.7) microg/L, Ke (0.329 +/- 0.057)/h, T1/2(2.2 +/- 0.4) h; High dose group: Ka (1.934 +/- 0.794)/h, tmax (1.7 +/- 0.3) h, Cmax (749.3 +/- 387.2) microg/L, AUC0-14(3820.1 +/- 1966.4) microg x h/L, Ke (0.373 +/- 0.174)/h, T1/2( 2.2 +/- 0.7) h. AUC of both erythromycin propionate and erythromycin base was linearly correlated to the doses; T1/2 was not correlated to the doses, so they followed the first order processes. The pharmacokinetic parameters of erythromycin The erythromycin stinoprate propionate and erythromycin base had no gender differences. Conclusion was absorbed as erythromycin propionate. Cmax reached at about 1.6 h. T1/2 of elimination was 2.4-3.1 h. The active component of erythromycin propionate was erythromycin. Cmax of erythromycin is 1.8, T1/2 is 2.4-3.1 h. In the range of oral dose of 250 to 750 mg, both erythromycin propionate and erythromycin base accorded the first order processes. The pharmacokinetic parameters were different with those reported in foreign documents while the gender difference did not exist in Chinese adults.

Aim: To study the multiple dose pharmacokinetics of quetiapine and its sulfoxide-, 7-hydroxy-, 7-hydroxy-N-dealkyl-metabolites in Chinese suffering from schizophrenia., Methods: Twenty-one patients (11 females and 10 males) were given quetiapine twice daily to control the symptoms. After the dose reached 200 mg twice daily, blood were sampled to study the pharmacokinetics. The plasma concentrations of quetiapine and its metabolites were assayed by HPLC-MS., Results: The main pharmacokinetic parameters of quetiapine, 7-hydroxy-N-dealkyl-quetiapine, quetiapine sulfoxide, and 7-hydroxy-quetiapine were as follows: tmax were 2.0 (0.3-5.0), 4.0 (1.5-6.0), 3.0 (0.5-5.0), and 3.0 (0.5-5.0) h respectively; t1/2 were (7+/-3), (9.4+/-2.7), (7+/-3), and (8+/-5) h, respectively; Cmax(SS) were (678+/-325), (19+/-5), (451+/-216), and (58+/-22) microg/L, respectively; Cmin(SS) were (51+/-68), (3.3+/-1.6), (35+/-36), and (5+/-4) microg/L, respectively; Cav(SS) were (295+/-144), (13+/-4), (209+/-71), and (28+/-9) micro/L, respectively; AUC(0-12)(SS) were (3,538+/-1 728), (153+/-44), (2,512+/-854), and (335+/-104) microg.h.L(-1), respectively; AUC(0-infinite)(SS) were (5,534+/-4 198), (287+/-107), (3,858+/-2 012), and (529+/-262) microg.h.L(-1), respectively; Ke were (0.11+/-0.03), (0.079+/-0.019), (0.11+/-0.03), and (0.103+/-0.028) h(-1), respectively; CL/F and V/F of quetiapine were (67+/-25) L.h(-1) and (672+/-394) L, respectively. The plasma concentrations for the four compounds reached a steady state within 48 h at the dose of 200 mg initiation. These parameters were not statistically different between genders., Conclusions: Quetiapine was absorbed quickly, distributed widely, and metabolized mainly to be quetiapine sulfoxide. The elimination speeds of quetiapine and its three metabolites were similar. Gender had no effect on the pharmacokinetics of quetiapine and its metabolites. The clinical dosage regime caused no drug accumulation.

Aim: To develop a high performance liquid chromatography-electrospray mass spectrometry (HPLC-MS/ESI) method for simultaneous determination of quetiapine and its sulfoxide-, 7-hydroxy-, 7-hydroxy-N-dealkyl-metabolites in human plasma., Methods: The HPLC separation of the compounds was performed on a Kromasil C18, (5 microm, 4.6 mm.150 mm) column, using water (formic acid: 1.70 mmol/L, ammonium acetate: 5.8 mmol/L)-acetonitrile (65:35) as mobile phase, with a flow-rate of 0.95 mL/min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and detected in the selected ion recording (SIR) mode. The samples were extracted using solid-phase extraction columns., Results: The calibration curves were linear in the ranges of 10-2000 microg/L for quetiapine, 1-200 microg/L for its metabolites, respectively. The average extraction recoveries for all the four samples were above 85 %. The methodology recoveries were much higher than 95 %. The intra-day and inter-day RSD are less than 15 %., Conclusion: The method is accurate, sensitive, and simple for study of pharmacokinetics and metabolic mechanism of quetiapine in patients at therapeutic dose.