Trimethoprim-sulphamethoxazole and thrombocytopenia.

Thrombocytopenia is an uncommon but serious side effect of the antimicrobial combination of trimethoprim and sulphamethoxazole. Thirty-one cases in seven years, including two deaths, have been reported to the Australian Adverse Drug Reactions Registry. Females were affected twice as frequently as males. In 70% of the patients platelet counts were 20x10(9)/L or less. Thrombocytopenia which is associated with this agent may occur at any age.