Effect of dimethyl sulfoxide on sulindac disposition in rats

Sulindac and dimethyl sulfoxide (DMSO) are both effective antiinflammatory agents in man. Since the sulfoxide moiety in these compounds is metabolized similarly, a biochemical interaction between the two drugs in vivo was thought to be possible. After iv injections of sulindac (5 mg/kg), plasma concentrations of sulindac, and its sulfide and sulfone metabolites, were measured in normal rats and in rats that had received, 30 min earlier, a single ip dose of DMSO (0.1, 0.5, or 1.0 ml). The half-life of sulindac (normally 94 min) was increased significantly by DMSO (0.1, 0.5, or 1.0 ml). The half-life of sulindac (normally 94 min) was increased significantly by DMSO (408 min after 1.0 ml of DMSO). Plasma sulfide metabolite levels were reduced in a dose-related manner by DMSO (93% reduction in peak concentration after 1.0 ml of DMSO). Sulfone metabolite concentration was also significantly diminished by the highest dose of DMSO. Similarly, DMSO was shown to decrease conversion of sulindac to sulfide and sulfone metabolites by rat liver enzymes in vitro. Sulfoxide reductase was more sensitive to DMSO inhibition than was sulfoxide oxidase both in vivo and in vitro. These data demonstrate that DMSO can significantly alter in vivo the formation of the pharmacologically active, sulfide metabolite of sulindac; therefore, concurrent use of DMSO and sulindac should be approached with caution.