Zolmed/Zolmed Forte Drug Interactions

For Sulfamethoxazole: The action of sulfonamides may be antagonized by p-aminobenzoic acid and its derivatives, particularly potassium aminobenzoate and the procaine group of local anesthetics.
Sulfamethoxazole and other sulfonamides may potentiate the effects of some drugs, such as oral anticoagulants, methotrexate, and phenytoin; this may be due to displacement of the drug from plasma protein binding sites or to inhibition of metabolism.
For Trimethoprim: Trimethoprim may increase serum concentrations of some drugs, including phenytoin, digoxin, procainamide, rosiglitazone, and repaglinidine, potentiating their effect. This may be due to competitive inhibition of renal excretion, decreased metabolism, or both. It has been suggested that trimethoprim may potentiate the effects of warfarin. Trimethoprim has been reported to reduce the renal excretion and increase blood concentrations of zidovudine, zalcitabine, and lamivudine. Trimethoprim and dapsone increase each other's serum concentrations, whereas rifampicin may decrease trimethoprim concentrations.