Poor rectal absorption of trimethoprim/sulphamethoxazole in treating Pneumocystis carinii pneumonia

A 24-year-old female with Hodgkin's disease and Pneumocystis carinii pneumonia was treated with trimethoprim/ sulphamethoxazole (TMP/SMX) tablets. Because treatment failure was feared owing to chronic emesis potentially resulting in incomplete drug absorption, the same TMP/SMX dose was administered by rectal suppositories after the 5th day of oral dosing. The relative fractions (rectal/oral) of the suppository dose absorbed for TMP and SMX were 3 0% and 19.5% respectively. When TMP/SMX treatment is required and the oral route is not practical, the investigational i.v. preparation should be obtained.