Decreased effect rifampin may reduce the plasma concentration of carvedilol by up to 70 ; decreased effect has also occurred with aluminum salts, barbiturates, calcium salts, cholestyramine, colestipol, nsaids, penicillins ampicillin , salicylates, and sulfinpyrazone due to decreased bioavailability and plasma levels; beta-blockers may decrease the effect of sulfonylureas.
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