UROTRAX

Sulfamethoxazole competitively inhibits the utilisation of para-aminobenzoic acid in the synthesis of dihydrofolate by the bacterial cell resulting in bacteriostasis.

Trimethoprim is a dihydrofolate reductase inhibitor, inhibiting the conversion of bacterial dihydrofolic acid to tetrahydrofolic acid, required for the synthesis of some amino acids. Its effects are considerably greater on the cells of micro-organisms than on the mammalian cells.

Phenazopyridine is excreted in the urine where it exerts a topical analgesic effect on the mucosa of the lower urinary tract. This action helps to relieve pain, burning, urgency and frequency. The precise mechanism of action is unknown.