Experience with isoxsuprine in the treatment of sickle cell crisis: a proposed mechanism of action.

An accidental clinical observation triggered this investigation into the possible beneficial effects of isoxsuprine in the treatment of painful sickle cell crisis. Twenty-four patients were studied with a total of 34 episodes of painful crisis. As they had all been previously treated by us we knew the duration of their crisis under conventional treatment, so that the two regimens with and without isoxsuprine could be compared. Isoxsuprine was administered in 3 successive steps: (1) as an IM injection (5-10 mg), (2) as a rapid IV infusion (1 mg/minute), and (3) as a slow, continuous IV infusion, (0.1-0.3 mg/minute). The results from this study suggest that isoxsuprine exerts in fact a remarkable action in sickle cell crisis by bringing about prompt relief in approximately 80% of the cases within 5 hours, and in 40% of the cases within 2 hours. There were only 2 cases of absolute failure. The hospitalization time was remarkably reduced and the use of narcotics was minimized. Side effects (tachycardia, palpitations, somnolence) have been observed mainly in cases where relatively high doses of isoxsuprine had to be administered IV.