infectious diseases
Trimethoprim and Sulfamethoxazole
Introduction
 is available as a single drug or in combination with sulfamethoxazole (a Sulfonamides ). The drugs act synergistically to block sequential steps in bacterial folate metabolism: Trimethoprim(TMP) prevents reduction of dihydrofolate to tetrahydrofolate. Sulfamethoxazole (SMX) inhibits conversion ofp-aminobenzoic acid to dihydropteroate. This synergy results in maximal antibacterial activity, which is often bactericidal. Trimethoprim/sulfamethoxazole (TMP/SMX) is available as a fixed combination consisting of a 1:5 ratio (80 mg TMP plus 400 mg SMX or a double-strength tablet of 160 mg TMP plus 800 mg SMX). 