[Optimization of the formulation of ranolazine hydrochloride sustained-release tablet and its pharmacokinetics in...

Ranolazine hydrochloride sustained-release tablet (RH-ST) was prepared and its release behavior in vitro was studied. The pharmacokinetic characteristics and bioavailability in six Beagle dogs after oral administration of RH-ST and ranolazine hydrochloride common tablets (RH-CT) as reference were compared. Three kinds of matrix, hydroxypropylmethylcellulose (HPMC K4M), ethylcellulose (EC 100cp) and acrylic resins (Eudragit RL100) were selected as functional excipients to keep ranolazine hydrochloride (RH) release for 12 hours. Through orthogonal designs, the polymers were quantified and the optimized cumulative release profile was obtained. The single oral dose of RH-ST 500 mg and RH-CT 333.3 mg was given to six dogs using a two way crossover design. Plasma levels were determined by LC-MS and the absorption fractions were calculated according to Loo-Riegelman formula. The steady-state concentration of RH in plasma of six dogs and its pharmacokinetics behaviors after continuous oral administration of RH-ST and RH-CT at different time intervals were studied by LC-MS. The steady-state pharmacokinetic parameters were computed by software program BAPP2.0. With the increase of the amount of the matrix, the drug release was decreased. The most important factor influencing drug release is the quantity of HPMC K4M. Drug release within the period (from 0 h to 12 h) fitted well into Higuchi model. The correlation coefficient (r) between the dissolution in vitro in release media of the distilled water and the absorptin fraction in vivo was 0.9550. To compare with RH-CT, RH-ST in vivo has a steady and slow release behavior, Tmax was obviously delayed (3.00 +/- 0.50) h and the relative bioavailability was over 80 percentage. The combined use of multiple polymers can decrease the tablet weight effectively, and the drug release rate can be decreased both in vitro and in vivo.