A drug of the sulfonamide group. It is taken by mouth and is effective in the treatment of infections of the respiratory tract (including bronchitis), the urinary and gastrointestinal tracts, and the skin. The drug is frequently administered in a combined preparation with trimethoprim.
Sulfamethoxazole has been used in combination with trimethoprim (as co-trimoxazole) to treat infections of the urinary tract. Increasing bacterial resistance to sulphonamides and the incidence of side-effects mean that caution is needed in prescribing co-trimoxazole.