Sulfinpyrazone drug interactions

Multiple drug interactions have been discribed (decreased serum concentrations of phenobarbital, phenytoin, sulfinpyrazone and rifampin, increased serum concentrations of quinidine, carbamazepine, cyclosporin). Important in this setting is that a marked interaction exists between digoxin and verapamil, increasing the serum concentrations of the former due to decreased renal excretion,... 

Drug interaction Stereoselective inhibition of the metabolism of (S)-warfarin by sulfinpyrazone coupled to a stereoselective increase in the elimination of (R)-warfarin... 

Caforio AL, Gambino A, Tona F, Feltrin G, Marchini F, Pompei E, Testolin L, Angelini A, Dalla Volta S, Casarotto D. Sulfinpyrazone reduces cyclosporine levels a new drug interaction in heart transplant recipients. J Heart Lung Transplant 2000 19(12) 1205-8. 

A review of the drug interactions of sulfinpyrazone identified two studies that found interactions with phenytoin. In the first, the serum phenytoin levels of 2 out of 5 patients taking phenytoin 250 to 350 mg daily were doubled from about 10 to 20 micrograms/mL within 11 days of starting to take sulfinpyrazone 800 mg daily. One of the remaining patients had a small increase in phenytoin levels, but the other two had no changes at all. When the sulfinpyrazone was withdrawn, the serum phenytoin concentrations fell to their former levels. The second study was a clinical study in epileptic patients that found that sulfinpyrazone 800 mg daily for a week increased the phenytoin half-life from 10 to 16.5 hours and reduced the metabolic clearance from 59 to 32 mL/minute. 

Perel JM, Dayton PG, Snell MM, Yu TF, Gutman AB. Studies of interactions among drugs in man at the renal level probenecid and sulfinpyrazone. Chn Pharmacol Ther 1969 10(6) 834-40. 

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