Interactions, drug sulfonamides, potentiated

Important drug interactions of the sulfonamides are seen with the oral anticoagulants, the sulfony-lureas, and phenytoin. In each case, sulfonamides can potentiate the effects of the other drug, either by inhibiting its metabolism or by displacing it from albumin. Dosage adjustment may be necessary. 

Supra-additive interactions and potentiation appear to be much less common than antagonism and the simple additive interactions described above. Supra-additive (synergistic) interaction is said to occur if the result of interaction is greater than the sum of the drugs used alone the best example is the therapeutic synergism of certain antibiotic combinations such as sulfonamides and dihydrofolic acid reductase inhibitors such as trimethoprim. Potentiation is said to occur when a drug s effect is increased by another agent that has no such effect. The best example of this type of interaction is the therapeutic interaction of beta-lactamase inhibitors such as clavulanic acid with lactamase-susceptible penicillins. 

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