Study on pharmacokinetics and bioavailability of nirendipine crystal polymorphs in rabbits

OBJECTIVE To study the pharmacokinetics and relative bioavailability of nitrendipine crystal polymorphs in rabbits.METHODS According to the Latin's design,6 rabbits were divided into 3 groups with cross-over design of oral nitrendipine administration I,II and Ⅲ capsules 80 mg·kg-1 respectively.The plasma concentrations were determined by HPLC.The pharmacokinetic parameters were calculated.RESULTS After a single oral dose,the peak plasma concentration(Cmax)of nitrendipine Ⅰ,Ⅱ and Ⅲ were(351.5±18.7),(392.7±50.8),(822.1±39.7)μg·L-1;the peak time(tmax)were(1.72±0.16),(1.83±0.11),(1.81±0.18)h;the half-time(t1/2)were(13.3±3.5),(8.6±1.2),(8.0±2)h;the area under curve(AUC0→t)were(3 635.1±230.8),(2 697.0±209.4),(6 428.6±585.6)h·μg·L-1,respectively.The relative bioavailability of nitrendipine Ⅱ,Ⅲ to nitrendipine Ⅰ were 62.1% and 169.0%.CONCLUSION There was no bioequivalence among nitrendipine polymorphs.