[Sustained-release pellet of vasodilators--basic experiment].

ABSTRACT

We examined the efficacy of slow-release, and prolonged diffusion silicone pellets mixed with papaverine hydrochloride in the treatment of cerebral vasospasms following subarachnoid hemorrhage. In addition the diffusion of the other vasodilating agents (diltiazem and nicardipine) into the saline solution using the same silicone materials was also investigated. Papaverine hydrochloride was either packed in silicone tubes (packed type) or polymerized with silicone elastomer, Silastic MDX-4-4210 (solid type). The solid type pellet is cylindrical-(diameter 3 mm, length 30 mm) and contains 40 w/v% of pure powder of papaverine. The amount of the delivered drug was measured for 5 weeks at 37 degrees C and at room temperature. The diffusion rate of the solid type pellet was about 5 times higher than that of the packed one. The diffusion rates of both types of pellets were about 10 times higher at 37 degrees C than at room temperature. The cummulative amount of the delivered drug from the solid type pellet was 37.1% of the initial packed volume at 37 degrees C in the first 3 weeks. The diffusion of diltiazem and nicardipine which were polymerized 30 w/v% in silicone elastomer was observed for 3 weeks at 37 degrees C only in solid type pellet form. The diffusion rate was measured under the condition of either continuous shaking or standing. The results showed the same diffusion rates for diltiazem and nicardipine, with no difference in diffusion rate between the "shaking" and "standing" groups. The diffusion rate showed inverse exponential curves, and was 5-20 X 10(-5)/day/mm2 of initial volume until 5 days.(ABSTRACT TRUNCATED AT 250 WORDS)