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Meisoindigo has been a routine therapeutic agent in the clinical treatment of chronic myelogenous leukemia (CML) in China since the 1980s. In the present study, the in vitro antileukemic activity of meisoindigo was investigated in acute promyelocytic leukemia (APL) cells, acute myeloid leukemia (AML) cells, and myelomonocytic leukemia cells (NB4, NB4.007/6, HL-60 and U937) comprising both retinoic acid-sensitive and retinoic acid-resistant cells. We found that meisoindigo effectively inhibited the growth and/or proliferation of these four cell types at µM levels. The effects of meisoindigo in these cells are related to its proliferation inhibition and apoptosis induction, and are independent of cell cycle arrest, indicating that meisoindigo could be possible in the treatment of APL, AML and retinoic acid resistant APL. The in vivo pharmacokinetics of meisoindigo and its major circulatory metabolites in rat plasma were then investigated by a newly developed and validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The profiles of plasma concentration versus time were plotted and the relevant pharmacokinetic parameters were calculated for meisoindigo and its reductive metabolites. The plasma concentrations of meisoindigo after oral administration were much lower than the in vitro IC50s determined in the leukemic cells. The contradicting poor pharmacokinetic characteristics and the established clinical efficacy of meisoindigo could indicate the presence of active metabolites in vivo.

All-trans-retinoyl-beta-D-glucuronide (RAG) is an endogenous active metabolite of all-trans-retinoic acid (ATRA). In the present study, the pharmacokinetics of RAG was examined after the administration of a single intravenous does (5, 10, or 15 micromol/kg) and of multiple daily intravenous doses (5 micromol/kg) to rats for 8 days. The plasma concentrations of RAG and ATRA were measured by a reverse-phase HPLC method. A rapid distribution phase of approximately 1 h was observed in all of the rats after single or multiple doses. Thereafter, RAG was eliminated through a first-order process, in accord with a typical two-compartment first order pharmacokinetic profile. After single intravenous doses, the AUC of RAG increased proportionally with the dose and the clearance remained unchanged within the tested doses. There was no statistical significant difference in distribution rate constants from central compartment to peripheral compartment (K(12)) and from peripheral compartment to central compartment (K(21)) between different doses. However, as the dose increased from 5 micromol/kg to 10 micromol/kg, the volume of distribution at the steady state (V(ss)) and the volume of peripheral compartment (V(p)) decreased significantly (p0.05) from 1.290 +/- 0.269, 0.928 +/- 0.232. L/kg to 0.961 +/- 0.149, 0.647 +/- 0.107 L/kg, respectively. V(ss) and V(p) at a dose of 15 micromol/kg (0.924 +/- 0.187, 0.698 +/- 0.165 L/kg) were not significantly different from that at 10 micromol/kg. Thus, RAG might saturate the tissue-binding sites at higher doses. ATRA was detected as a metabolite of RAG at low levels (usually0.05 microM) only in the first 2 h after intravenous administration. RAG clearly was not extensively hydrolyzed to ATRA in our study. After multiple daily intravenous administration of RAG, the clearance (Cl) and the elimination rate constant (K(10)) remained unchanged (p0.05), indicating that long-term daily administration of RAG did not induce its accelerated metabolism. However, K(12), V(p), and V(ss) declined significantly (p0.05) from 1.67 +/- 0.54 h(-1), 0.928 +/- 0.232 L/kg, and 1.290 +/- 0.269 L/kg to 0.96 +/- 0.48 h(-1), 0.494 +/- 0.147 L/kg, and 0.818 +/- 0.187 L/kg, respectively. Therefore, long-term daily dosing of RAG seemed to decrease its distribution profile. Although the AUC of RAG did not change significantly after multiple dosing, the AUC of ATRA after RAG dosing significantly declined (p0.05) from 0.032 +/- 0.019 microM x h to 0.010 +/- 0.006 microM x h. The decline in the AUC of ATRA might reflect an increase in its uptake by tissue and/or in its metabolism. Because enhanced clearance is not associated with RAG after multiple administrations, RAG could be considered as an alternate to ATRA in appropriate clinical applications.

Background All-trans-retinoic acid (ATRA, vitamin A acid or tretinoin) is effective in the treatment of acute promyelocytic leukaemia (APL). Unfortunately, the oral absorption of ATRA is highly variable. Its poor aqueous solubility also makes it difficult to be formulated into parenteral formulation. To date, there is no parenteral formulation of ATRA available commercially. Objective To undertake the preformulation work necessary for developing such a product. Method We investigated the solubility and stability profile of ATRA in various formulations. Results The aqueous solubility of ATRA could be greatly increased by the inclusion of ATRA in 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD). Adjusting the pH value further improved the water solubility of ATRA. The photostability of HP-beta-CD-based formulation of ATRA was evaluated and it was found that inclusion ATRA into HP-beta-CD did improve the photostability of ATRA. Conclusion These results showed that it is possible to develop a parenteral formulation and/or an aqueous oral formulation of all-trans-retinoic acid by using 2-hydroxypropyl-beta-cyclodextrin. However, the biopharmaceutical properties of such a formulation would be necessary before its use.

all‐trans‐Retinoic acid (ATRA, vitamin A acid, or tretinoin) is a potent chemotherapeutic agent for the treatment of acute promyelocytic leukemia (APL). Its poor aqueous solubility not only affects its oral absorption but also prevents it from forming an aqueous parenteral formulation. Recently, we developed a water‐soluble formulation of ATRA with 2‐hydroxypropyl‐β‐cyclodextrin (HPβCD). In present study, this formulation was tested in Sprague‐Dawley rats. Kinetic study of ATRA was carried out after oral or intravenous administration. Though there were no statistical differences in any of the estimated pharmacokinetic parameters between ATRA sodium salt and HPβCD‐based ATRA after intravenous administration, inclusion of ATRA into HPβCD was found to greatly improve the oral absorption of ATRA. © 2000 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89: 260–267, 2000

Quantum dots (QDs) possess unique properties that are expected for various applications. Herein, realgar (As4S4) QDs were synthesized via a wet chemical method in a coordinating solvent (e.g., ethanolamine (EA)) with assistance of an acid (e.g., citric acid (CA)). The as-prepared realgar QDs using EA and CA have a narrow size distribution with a mean value of 5.48[Formula: see text]nm and a relative standard deviation of [Formula: see text]20%, and exhibit bright photoluminescence (PL) in a short wavelength window ([Formula: see text] 480[Formula: see text]nm) with high quantum yield up to 70%. Moreover, realgar QDs can retain their high PL after one-year storage, indicating their excellent stability. Bulk realgar is a commonly used traditional medicine, however, its water-insolubility limits its broad applications. Realgar QDs could be an alternative for the bulk realgar owing to their excellent water-solubility and efficient PL. In preliminary in vivo toxic and pharmaceutical experiments, the synthesized realgar QDs at a single oral dose of 10.0[Formula: see text]mg realgar/kg body weight for 21 days showed tolerability in healthy mice and effective against tumor-bearing nude mice, respectively. In this study, assembly of realgar QDs into specific hollow nanospheres was first constructed by introducing an acid into their original colloidal solution. Simple dissolution of such assemblies in EA can partially return them into the fluorescent QDs. Such property is desired for a variety of media-responsive luminescence materials. In addition, a flexible inorganic/organic hybrid composite film was fabricated for the first time by incorporation of realgar QDs into polyvinyl alcohol matrix. The resulting film presents excellent PL, good transparency, intense mechanical strength and facile processibility, which meet the requirements for device integration.

Ginsenoside Rh4 (Rh4) and ginsenoside Rk3 (Rk3) are two active substances isolated from the processed Panax species. To further explore their potential medicinal application, a reliable liquid chromatography-tandem mass spectrometry method (LC/MS/MS) was developed and validated for the quantification of Rh4 and Rk3 in rat plasma. Multiple ion monitoring and multiple reaction monitoring experiments were performed in negative ionization mode. This LC/MS/MS method had good selectivity, sensitivity (lower limit of quantification = 10 ng/mL), precision (intra- and inter-day relative standard deviation ≤ 10.1) and accuracy (analytical recovery within 100 ± 10%). The pharmacokinetic profiles of Rh4 and Rk3 were subsequently assessed in Sprague-Dawley rats. Similar to many other ginsenosides, the oral bioavailability of Rh4 and Rk3 was unfavorable, and Rh4 and Rk3 did not have any measurable plasma exposure after oral administration (20 mg/kg). Fortunately, upon intravenous administration (5 mg/kg), both Rh4 and Rk3 possessed abundant plasma exposure, moderate clearance (Cl = 50.2 ± 7.7 and 23.8 ± 1.4 mL·min(-1)·kg(-1), respectively) and terminal elimination half-life (t(1/2 λZ) = 157.2 ± 65.2 and 99.5 ± 37.8 min, respectively). As Rh4 and Rk3 displayed favorable intravenous pharmacokinetic profiles, further exploration on their medicinal application is warranted.

Scope Pterostilbene (trans-3,5-dimethoxy-4'-hydroxystilbene, PTS) possesses various health-promoting effects. This study aimed to investigate the impacts of aqueous solubility, fasting, dose escalation, and dosing route on its bioavailability in Sprague-Dawley rats. Methods and results Upon intravenous administration (2.5 mg/kg), PTS had rapid clearance (Cl = 68.2 ± 9.8 mL/min/kg) and moderate terminal elimination half-life (t1/2λz = 93.9 ± 22.3 min). Dose-escalation led to about twofold decline in clearance at the dose of 25 mg/kg (Cl = 36.4±7.8 mL/min/kg). When given in oral suspension (15 mg/kg), PTS had relatively low bioavailability (F = 15.9 ± 7.8%) while fasting substantially attenuated its bioavailability (F< 5.5 %). However, when dosed in a solution formulated with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) (15 mg/kg), PTS possessed good bioavailability (F = 59.2 ± 19.6%). Dose escalation resulted in about twofold increase in bioavailability at the dose of 60 mg/kg. Sublingual delivery (2.5 mg/kg) led to rapid absorption and moderate bioavailability (F = 25.8 ± 13.1%). Statistical comparison clearly indicated that the pharmacokinetics of PTS was more favorable than resveratrol. Conclusion Aqueous solubility was identified as a barrier to its oral bioavailability while solubilizing PTS with HP-β-CD substantially increased its bioavailability; dose manipulation was a practical strategy to enhance its bioavailability and systemic exposure; and its delivery through oral mucosa was feasible. As PTS possessed superior pharmacokinetics, it is a favorable candidate for further development.

Histone deacetylase inhibitors (HDACIs) belong to an emerging class of anticancer compounds. It is increasingly recognized that their unique and complementary mode of action make HDACIs valuable agents in augmenting the cytotoxicity of conventional chemotherapeutics. We examined the potential for combined use of an approved HDACI, suberoylanilide hydroxamic acid (SAHA), with cisplatin (Cddp) in platinum-resistant ovarian cancer cells, OVCAR-3 and SKOV-3. The nature of the drug interaction following combinatory therapy was assessed using median effect analysis. We found that SAHA acted synergistically with Cddp over a wide range of concentrations in both cell types, resulting in favorable dose reductions of both compounds. In particular, in the more Cddp-resistant SKOV-3 cells, more than 8-fold dose reduction of Cddp was achieved with the simultaneous use of SAHA and Cddp as compared to the dose required to elicit similar cell kill effects using Cddp alone. More importantly, therapeutic selectivity for ovarian cancer cells over normal fibroblast cells were maintained with the combinatorial therapy. We further observed that the augmentation of Cddp-induced cell death was mediated by the net increase in apoptosis and was independent of cell cycle arrest. Overall, concurrent application of SAHA and Cddp yielded the most favorable cell kill, indicating that this combination is promising for treatment of platinum-resistant ovarian tumors.

trans-2,4,3′,4′,5′-Pentamethoxystilbene (2,4,3′,4′,5′-PMS) is a resveratrol derivative that displayed promising pre-clinical anti-cancer activities. In this study, a simple HPLC method was developed and validated to determine 2,4,3′,4′,5′-PMS in rat plasma. The lower limit of quantification was 9 ng/ml. The intra- and inter-day precision in terms of relative standard deviation was less than 9.7% and the bias rate ranged from −6.4 to +7.8%. The pharmacokinetics of 2,4,3′,4′,5′-PMS was subsequently studied in Sprague-Dawley rats. Upon intravenous administration (0.75 mg/kg), 2,4,3′,4′,5′-PMS displayed moderate clearance (58.5 ± 19.5 ml/min/kg) and terminal elimination half-life (147 ± 61 min). Aqueous solubility appeared to be a barrier to oral absorption. When suspension was given (4 mg/kg), the absolute oral bioavailability was almost nil; when 2,4,3′,4′,5′-PMS was fully solubilized by randomly methylated-β-cyclodextrin, it possessed a low bioavailability (3.63 ± 2.06%). The pharmacokinetic comparison among 2,4,3′,4′,5′-PMS and other methoxylated stilbenes suggested that the 2-methoxy group was unfavorable to oral bioavailability. Future investigations on 2,4,3′,4′,5′-PMS should be focused on chemo-prevention of colorectal carcinogenesis.

We propose using dried blood spots (DBS) as sample matrix for gas chromatography/mass spectrometry (GC/MS) based metabolomic profiling for the benefits of higher sample stability, more convenient sample acquisition with DBS, higher analyte separation power, and more readily biomarker identification with GC/MS. To establish this proposition, the metabolomic profiles generated from DBS were compared with that obtained from the conventional whole blood and plasma matrixes and also with dried plasma spots (DPS) as another covariate control. Our findings indicated that whole blood produced the most number of detectable markers (866), whereas DPS yielded the least number (614). DBS and plasma matrix, on the other hand, produced the most similar numbers of detectable (695 vs 749) and identifiable markers (137 vs 147, matching with Fiehn library). From the analysis of the DBS and plasma metabolomic profiles, it was concluded that when l-lysine 2, iminodiacetic acid 2, dl-threo-beta-hydroxyaspartic acid, citric acid, or adenosine-5-monophosphate 2 are not involved as markers, DBS could be a suitable substitute for plasma for metabolomic profiling.

α- and β-Amyrins are naturally occurring triterpenes with a wide range of biological activities. In this study, a reliable GC-MS method was developed and validated for the quantification of α- and β-amyrins in rat plasma. The calibration curves were linear (R(2) > 0.996) with a limit of quantification of 1.0 ng ml(-1) for both α- and β-amyrins. The precision and repeatability of this method was good as the relative standard deviation were 12% or less. The absolute recovery ranged from 71% to 89%, while the analytical recovery ranged from 95% to 99%. The pharmacokinetic profiles of α- and β-amyrins in rats were subsequently investigated in Sprague-Dawley rats. β-Amyrin was administered intravenously and also orally in two forms, namely, as a suspension of the pure compound and the crude plant extract. α-Amyrin was administered orally as a suspension of the crude plant extract. β-Amyrin had a very long terminal elimination half-life (t(1/2λz) = 610 ± 179 min) and extremely slow clearance (Cl = 2.04 ± 0.24 ml min(-1) kg(-1)). The absolute oral bioavailability of β-amyrin in the crude plant extract was about fourfold higher than that in the suspension of pure form (3.83% vs 0.86%). When given in crude plant extract, both α- and β-amyrins had a similar dose normalized C(max). This reliable GC-MS method will enable further pharmacokinetic investigations of α- and β-amyrins.

A rapid HPLC method was developed and validated for the quantification of oxyresveratrol analog trans-2,4,3′,5′-tetramethoxystilbene (oxyresveratrol tetramethyl ether, OTE) in rat plasma. Chromatographic separation was achieved on an RP-HPLC column, which was protected by a guard column through a 12 min gradient delivery of a mixture of acetonitrile–water at 50°C. The UV absorbance at 325 nm was recorded. The retention time of OTE and trans-stilbene (internal standard) was about 7.7 and 8.4 min, respectively. The calibration curves were linear (R2 ≥ 0.9986) with a lower limit of quantification of 15 ng/mL. The intra- and inter-day variations, in terms of RSD, were all lower than 9.8% while the intra-day and inter-day bias ranged from −8.3 to +9.2%. The pharmacokinetics of OTE was assessed in rats using 2-hydroxypropyl-β-cyclodextrin as a dosing vehicle. After intravenous administration, OTE possessed a long terminal elimination half-life (t1/2λz = 481 ± 137 min) and slow clearance (Cl = 29.1 ± 3.7 mL/min/kg). Upon oral administration, OTE was rapidly absorbed. However, it only displayed minimal plasma exposure and its absolute oral bioavailability (F) was as low as 4.5 ± 3.2%. Fortunately, the levels of OTE after single oral administration were sufficient to inhibit human cytochrome P450 1B1. Copyright © 2010 John Wiley & Sons, Ltd.

A simple HPLC method had been developed and validated to quantify Z -3,5,4′-trimethoxystilbene ( Z -TMS), a phyto-stilbene with potent anti-cancer activities in rat plasma. Chromatographic separation was achieved on a reversed phase-HPLC column, which was protected by a guard column through a 13.5-min gradient delivery of a mixture of acetonitrile and water at a flow rate of 1.5 ml/min at 50 °C. The UV absorbance at 300 nm was recorded. Z -TMS and E -stilbene (internal standard) eluted at 8.8 and 9.3 min, respectively. The calibration curve was linear within the range of 33–2500 ng/ml ( R 2 > 0.9995) and 10 ng/ml was the lower limit of detection. The intra- and inter-day precisions were good and the relative standard deviation was all lower than 10%. The analytical recovery of Z -TMS in plasma ranged from 94.6 ± 9.1% to 97.0 ± 2.1%. This HPLC method was successfully applied to assess the pharmacokinetic profile of Z -TMS in Sprague–Dawley rats using hydroxypropyl-β-cyclodextrin (HP-β-CyD) as a dosing vehicle. Although Z -TMS displayed negligible oral bioavailability, it had a fairly long terminal elimination half-life, abundant plasma drug exposure and limited clearance following intravenous administration. As Z -TMS had favorable intravenous pharmacokinetic profile, further investigation on its potential as a cancer chemotherapeutic agent is warranted.

A simple and sensitive HPLC-UV method was developed and validated for the quantification of piceatannol analog trans -3,5,3′,4′-tetramethoxystilbene (M-PIC) in rat plasma. Following protein precipitation with three volumes of acetonitrile, the analytes were separated on a RP-HPLC column, which was protected by a guard column through gradient delivery of a mixture of acetonitrile–water at 40 °C. The UV absorbance at 325 nm was recorded to quantify M-PIC. The retention time of M-PIC and trans -3,5-dimethoxystilbene (internal standard) was 7.4 and 8.4 min, respectively. The calibration curves were linear ( R 2 > 0.9989) with a lower limit of quantification of 15 ng/ml. The intra- and inter-day precisions, in terms of RSD, were all lower than 7.5%. The average analytical recovery ranged from 97.0 to 104.3% while the average absolute recovery ranged from 101.8 to 105.0%. This reliable HPLC method was subsequently applied to assess the pharmacokinetic profile of M-PIC in Sprague–Dawley rats using 2-hydroxypropyl-β-cyclodextrin as a dosing vehicle. The terminal elimination half-life ( t 1/2λz ) and clearance (Cl) of M-PIC were 313 ± 20 min and 33.1 ± 3.9 ml/min/kg, respectively; and its absolute oral bioavailability was as high as 50.7 ± 15.0%. M-PIC appeared to have a favorable pharmacokinetic profile and further pharmacological investigation on this phyto-stilbene was warranted.

A simple HPLC-UV method was developed and validated for the quantification of pterostilbene (3,5-dimethoxy-4'-hydroxy-trans-stilbene), a pharmacologically active phytoalexin in rat plasma. The assay was carried out by measuring the UV absorbance at 320 nm. Pterostilbene and the internal standard, 3,5,4'-trimethoxy-trans-stilbene eluted at 5.7 and 9.2 min, respectively. The calibration curve (20-2000 ng/mL) was linear (R(2)> 0.997). The lower limits of detection and of quantification were 6.7 and 20 ng/mL, respectively. The intra- and inter-day precisions in terms of RSD were all lower than 6%. The analytical recovery ranged from 95.5 +/- 3.7 to 103.2 +/- 0.7% while the absolute recovery ranged from 101.9 +/- 1.1 to 104.9 +/- 4.4%. This simple HPLC method was subsequently applied in a pharmacokinetic study carried out in Sprague-Dawley rats. The terminal elimination half-life and clearance of pterostilbene were 96.6 +/- 23.7 min and 37.0 +/- 2.5 mL/min/kg, respectively, while its absolute oral bioavailability was 12.5 +/- 4.7%. Pterostilbene appeared to have better pharmacokinetic characteristics than its natural occurring analog, resveratrol.

Histone deacetylase (HDAC) inhibitors are a new family of anti-cancer agents currently undergoing clinical investigations for various oncology indications. Their anti-inflammatory activities had been well documented and they appear to be potential therapeutic strategies for various inflammatory diseases. In this review, the anti-inflammatory activities of HDAC inhibitors with emphasis on their potential applications in rheumatoid arthritis (RA) will be summarized. The possible anti-rheumatic mechanisms, including growth arrest in rheumatoid arthritis synovial fibroblasts (RASFs), suppression of pro-inflammatory cytokines or chemokines, anti-angiogenesis as well as protective effects on bone and cartilage destruction will also be discussed. Current literatures strongly imply HDAC inhibitors as innovative anti-rheumatic drug candidates. However, long-term safety is a major concern. Future investigations should focus on identification of molecular anti-rheumatic mechanisms, development of new classes of HDAC inhibitors with better safety and selectivity profiles, combination of HDAC inhibitors with disease modifying anti-rheumatic drugs (DMARDs) and establishment of topical or intra-articular formulations.

This study aimed at the investigation of the impact of aqueous solubility and dose manipulation on the pharmacokinetics of resveratrol.Water soluble intravenous and oral formulations of resveratrol were prepared with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and randomly methylated-beta-cyclodextrin (RM-beta-CD), respectively. Sodium salt and suspension of resveratrol in carboxymethyl cellulose (CMC) were used as the reference intravenous and oral formulations, respectively. The pharmacokinetics of resveratrol was assessed in Sprague-Dawley rats. Plasma resveratrol concentrations were measured by high performance liquid chromatography (HPLC).Both HP-beta-CD and RM-beta-CD enhanced the aqueous solubility of resveratrol. After intravenous administration, rapid elimination of resveratrol was observed at all tested doses (5, 10, and 25 mg kg(-1)) regardless of formulation types; with non-linear elimination occurring at the dose of 25 mg kg(-1). RM-beta-CD significantly increased the maximal plasma concentration of orally administered resveratrol, but, it did not increase the oral bioavailability in comparison with the CMC suspension. Furthermore, the oral bioavailability remained unchanged among all tested doses (15, 25, and 50 mg kg(-1)).Aqueous solubility barrier might affect the speed but not the extent of resveratrol absorption. Further, dose manipulation (up to 50 mg kg(-1)) did not have a significant impact on the oral bioavailability of resveratrol.

8-Hydroxy-2´-deoxyguanosine (8OHdG) is a widely used biomarker for the measurement of endogenous oxidative DNA damage. A sensitive method for the quantification of 8OHdG in urine by single solid-phase extraction and GC-MS (gas chromatography with MS detection) using selective ion monitoring is described in the present study. After solid-phase extraction, samples are freeze-dried, derivatized by trimethylsilylation and analysed by GC-MS. The urinary 8OHdG was quantified using heavy isotope dilution with [18O]8OHdG. The recovery of 8OHdG after the solid-phase extraction ranged from 70 to 80% for a wide range of urinary 8OHdG levels. Using 1 ml of urine, the limit of quantification was >2.5 nM (2.5 pmol/ml) and the calibration curve was linear in the range 2.5–200 nM. This method was applied to measure 8OHdG in urine samples from 12 healthy subjects. The intra- and inter-day variations were

Acitretin, an active metabolite of etretinate, is as effective as etretinate in the treatment of psoriasis. Recently, we developed some water-soluble formulations of acitretin with 2-hydroxypropyl-beta-cyclodextrin (HPBCD)/randomly substituted methyl-beta-cyclodextrin (RMBCD). In this study, the biopharmaceutic properties of these formulations were tested in Sprague-Dawley rats. After single intravenous dosing (2.5, 5, or 10 mg/kg) with the HPBCD-based formulation, the area under the plasma concentration-time curve of acitretin increased proportionally with the dose and its clearance remained unchanged within the tested dose range. We also found that the RMBCD-based formulation of acitretin improved its bioavailability and decreased the variations in various pharmacokinetic parameters. The improved biopharmaceutic properties of RMBCD-based acitretin might be attributed to its enhanced aqueous solubility. The elimination of acitretin through bile excretion was also studied. Our results indicated that the major fraction of acitretin (approximately 40%) was excreted in the bile as beta-glucuronide conjugate and only trace amounts were excreted as unconjugated acitretin (approximately 0.5%). This finding further confirmed the importance of conjugated metabolism and biliary excretion in the elimination of this drug.

Acitretin, a retinoid for the treatment of severe psoriasis, exhibits extremely low aqueous solubility and high photosensitivity. This study investigated the effects of the complexation of acitretin with the respective hydroxypropyl-β-cyclodextrin (HPBCD) and randomly substituted methyl-β-cyclodextrin (RMBCD) on the aqueous solubility and photostability of the drug. Phase-Solubility studies indicated that the solubility of acitretin was dramatically improved by formation of complexes and further increased by pH adjustment. Stability constants were much higher for acitretin complexed with RMBCD than with HPBCD. Both cyclodextrins acted to decrease degradation of acitretin in solution. The physicochemical properties of solid inclusion complexes were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffractometry. Molecular modeling with MMFF94s force field (SYBYL V6.6) was utilized to predict the preferred orientation of acitretin in the cyclodextrin cavity and the main structural features responsible for the enhancement of its solubility and photostability. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2449–2457, 2003