Comparison of soft gelatin capsule vs. sustained release formulation of papaverine HCl: vasodilation and plasma levels.

The vasodilatory action, plasma papaverine levels achieved, and the incidence of side effects after oral administration of papaverine hydrochloride as a soft gelatin capsule, were compared to those of a sustained release formulation. The incidence of side effects observed after 150 mg, two or three times per day, of the soft gelatin capsule was similar to that observed after 150 mg, twice per day, of the sustained release form in 15 patients with arteriosclerosis obliterans. A relatively higher plasma papaverine concentration was achieved, 120 minutes after 150 mg administration of the soft gelatin form, compared to an equivalent dose of the sustained release form. The degree of vasodilation obtained after four doses (150 mg X 4) of soft gelatin within 24 hrs., was significantly superior than that induced after four doses (150 mg X 4) of the sustained release form in 6 patients with a severe degree of arteriosclerosis obliterans.