Calcium-channel blockers + Sulfinpyrazone - Drug Interactions

Clinical evidence,mechanism, importance and management

A study in 8 healthy subjects found that sulfinpyrazone 800mg daily for a week, increased clearance of a single oral dose of verapamil by about threefold, possibly due to an increase in its liver metabolism (See reference number 1). The clinical importance of this is uncertain,but be alert for reduced verapamil effects. It seems probable that dosage may need to be increased.

1. Wing LMH,Miners JO, Lillywhite KJ. Verapamil disposition—effects of sulphinpyrazone andcimetidine. Br J Clin Pharmacol (1985) 19, 385–91.