Systematic development of a bioanalytical UPLC-MS/MS method for estimation of risperidone and its active metabolite in long-acting microsphere formulation in rat plasma

A systematic approach to develop a UPLC-MS/MS method was applied for quantifying of risperidone (RISP), its active metabolite, 9-hydroxy risperidone (9-OH-RISP) and internal standard (propranolol) in rat plasma. Liquid liquid extraction was performed using methyl tert-butyl ether for quantification of drug and its active metabolite by MS detection in the positive ion mode. Acquity UPLC system with BEH C18 (2.1 mm x 100 mm, particle size 1.7 mu m) column was used along with acetonitrile (0.1% formic acid)-2 mM (milli mole) ammonium acetate in isocratic condition was used as the mobile phase. Detection was performed by multiple reactions monitoring with precursor-to-product ion transitions with m/z 411.2-* 191.0 for RISP, m/z 427.2-* 207.0 for 9-OH-RISP and m/ z 260.1-* 116.0 for IS. The method was validated as per the FDA guidance on bioanalytical method validation. Linearity (r(2) = 0.999) was observed in the drug concentration ranging between 0.1 and 50 ng mL(-1), while all other parameters were found to be within the acceptable ranges. Method robustness was optimized by BoxBehnken design to monitor the influential variables to achieve maximal recovery of the analytes in the rat plasma. Pharmacokinetic evaluation of the analytes from long-acting microparticles in rat plasma showed two peaks indicating an initial burst effect within 24 h of administration followed by controlled drug release pattern upto 45 days, while marketed formulation (Risperdal Consta (R)) showed no plasma concentration during the lag time of 21 days followed by maximal drug absorption between 28 and 40 days.