Bioavailability, tissue distribution and excretion studies of a potential anti-osteoporotic agent, medicarpin, in female rats using validated LC-MS/MS method.

Medicarpin, one of the active constituents isolated from the extract of Butea monosperma, has been shown to have various pharmacological activities including potent anti-osteoporotic properties. The aim of this study was to investigate the oral pharmacokinetics, tissue distribution and excretion of medicarpin following single oral dose administration in female rats. Oral pharmacokinetics was explored at 5 and 20 mg/kg while tissue distribution, urinary and fecal excretion were studied following 20 mg/kg oral dose. Medicarpin was quantified in rat plasma, urine, feces and tissue samples using a validated LC-MS/MS method following reverse-phase HPLC separation on RP18 column (4.6 mm × 50 mm, 5.0 µm) using methanol and 10 mM ammonium acetate (pH 4.0) as mobile phase in the ratio of 80:20 (v/v) at a flow rate of 0.8 mL/min. The oral bioavailability of medicarpin was found to be low with low systemic levels. The concentration in tissues was significantly higher than plasma. Highest tissue concentrations were found in the liver followed by bone marrow. Urinary and fecal excretion of medicarpin was < 1 %. In conclusion, medicarpin was found to be highly distributed in body tissues and minimally excreted via urine or feces.

Species differences between rat and human in vitro metabolite profile, in vivo predicted clearance, CYP450 inhibition and CYP450 isoforms that metabolize benzanthrone: Implications in risk assessment.

Benzanthrone (BNZ) is a polycyclic aromatic hydrocarbon found in industrial effluent causing skin, respiratory, gastrointestinal, genitourinary, nervous and hemopoietic toxicity. While its toxicity has been well studied, its metabolism in humans has not been investigated. The aim of this study was to characterize species differences in the in vitro metabolism of BNZ in rat and human liver microsomes and to identify the CYP isoforms involved in its metabolism. Upon incubation in liver microsomes, BNZ was found to be a direct substrate of phase I metabolism in both rat and human, undergoing oxidation and reduction. The Km in rat, 11.62 ± 1.49 µM, was two-fold higher than humans (5.97 ± 0.83 µM) suggesting higher affinity for human CYPs. Further, incubation with human rCYPs, BNZ was found to be substrate of multiple CYPs. The predicted in vivo hepatic clearance was 63.55 and 18.91 mL/min/kg in rat and human, respectively, indicating BNZ to be a high clearance compound. BNZ was found to be a moderate inhibitor of human CYP1A2. BNZ metabolism by multiple CYPs indicates that single enzyme genetic polymorphism is unlikely to have profound effect on the toxicokinetics of BNZ and default uncertainty factor of 3.16 might be sufficient to capture the intraspecies kinetic variability.

Simultaneous determination of centchroman and tamoxifen along with their metabolites in rat plasma using LC-MS/MS.

AIM: Tamoxifen and centchroman are two non-steroidal, selective estrogen receptors modulators, intended for long term therapy in the woman. Because of their wide spread use, there is a possibility of co-prescription of these agents. MATERIALS & METHODS: We studied the probable pharmacokinetic interaction between these agents in breast cancer model rats. A simple, sensitive and rapid LC-ESI-MS/MS method was developed and validated for the simultaneous determination of tamoxifen, centchroman and their active metabolites. RESULTS: The method was linear over a range of 0.2-200 ng/ml. All validation parameters met the acceptance criteria according to regulatory guidelines. CONCLUSION: LC-MS/MS method for determination of tamoxifen, centchroman and their metabolites was developed and validated. Results show the potential of drug-drug interaction upon co-administration these two marketed drugs.