Abstract: AIM： To investigate timed-release tablets as to its timed-release effects both in vitro and in vivo. METHODS: Nicardipine hydrochloride was used as the model drug. The timed-release tablets were prepared by means of dry compression coating techniques. Two time parameters t_0.1 and t_0.8 were first presented and used to evaluate the influences of factors, such as the amount of PEG6000, the grade of ethylcellulose viscosity, tablet outercoat thickness and tablet hardness, on nicardipine release. The drug release mechanism was assured by an erosion experiment. Human pharmacokinetics was studies in five male volunteers using HPLC. RESULTS: In vitro the timed release tablets began to release the drug at about (6.5±0.3) h and ended at about (8.0±0.3) h; for the timed-release tablets and the normal tablets in vivo, the tmax and lag time were (8.3±0.4) h, (1.3±0.4) h and (6.4±0.3) h and (0.4±0.04) h, respectively. The comparative bioavailability of the timed-release tablets over the normal tablets was 93.6%±8.8%. CONCLUSION: The timed-release effects of nicardipine timed-release tablets were significant both in vitro and in vivo.