Quantification of rimonabant in rat plasma by high performance liquid chromatography and its application to pharmacokinetic studies
A rapid, simple, and sensitive high performance liquid chromatographic method with UV detection was developed and validated for the determination of rimonabant (RMT) from rat plasma. The retention behavior of RMT and zolpidem tartrate (ZPT, internal standard-IS) as a function of mobile phase pH, composition and flow rate was investigated. Separation was developed on a reverse-phase Gemini C18 column (150mm×4.6mm i.d., 5µm particle size), using a mixture of methanol (MET): water (0.05% Triethylamine (TEA), pH-7 adjusted with ortho phosphoric acid) in the ratio of 75:25 (%v/v) at a flow rate of 1.0 ml/min with UV detection at 252 nm within 10 min, and quantified based on drug/IS peak area ratios. The plasma samples were prepared by using liquid-liquid extraction, yielding more than 97.86% extraction efficiencies. The calibration curve was linear (correlation coefficient of 0.9992) in the concentration range of 25-25000 ng/ml. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 6.91 and 22.70 ng/ml, respectively. Both the intra-day and inter-day precisions at four tested concentrations were below 1.42% R.S.D. The present method was selective enough to analyze RMT in rat plasma without any tedious sample clean-up procedure and can be successfully applied for estimating the pharmacokinetic parameters of RMT following oral administration of a single 5 mg RMT to white albino rats.
Keywords : Pharmacokinetic studies, Rat Plasma, Rimonabant, RP-LC, SPE, Validation