OBJECTIVE: To enhance the dissolution rate and efficacy of nimodipine (NMDP) which is a poorly water-soluble substance, and to design the formulations with fast-release properties. METHOD: NMDP-PVP-k30 coprecipitate and physical mixture were prepared. The physical states of NMDP in both newly-made and one-year-old samples were investigated by X-ray diffraction analysis. The dissolution rates of NMDP from coprecipitate and from physical mixture were also compared. Five formulations were prepared on the basis of NMDP-PVP-k30 coprecipitate and their in vitro drug dissolution behaviors were examined. Also, the dissolution property of the capsules with one selected composition was examined. The selected capsules were compared with two commercial tablets on their drug release processes. RESULTS: NMDP-PVP-k30 coprecipitate gave much higher improvement in the dissolution rate than the physical mixture, and NMDP was released 89% from the coprecipitate and 45% from the physical mixture in five minutes respectively. There was no appearance of crystallization in the coprecipitate after one year storage under experimental conditions. The tablet formulation with the highest drug dissolution rate was selected. The capsules with the same composition as the selected tablet showed a higher drug dissolution rate, which indicated that drug release property was influenced by the compressing pressure. The results showed that the dissolution rate of NMDP from the selected capsules was about three to four times of that from the two commercial tablets.CONCLUSION: The dissolution rate of NMDP can be improved greatly by coprecipitation using PVP-k30 as a carrier.