Drug absorption may be greater if food is withheld for a few hours prior to dosing.

Sulfadiazine (SDZ) inhibits the incorporation of para-aminobenzoic acid into folic acid, and trimethoprim (TMP) inhibits the enzyme dihydrofolate reductase (DHFR) which converts dihydrofolic acid into tetrahydrofolic acid. Trimethoprim and sulfadiazine act together synergistically with a double-blockage mode of action. The combination is bactericidal, inhibiting sequential steps in the synthesis of purines which are required for DNA synthesis. TMP-SDZ combinations have a broad bactericidal action against many gram-positive and gram-negative aerobic bacteria and a large proportion of anaerobic bacterial.