Adverse effects of trimethoprim–sulfamethoxazole for the prophylaxis of Pneumocystis pneumonia in dermatology

Trimethoprim-sulfamethoxazole (TMP/SMX) combination is used for the prophylaxis of Pneumocystis pneumonia (PCP). Although TMP/SMX is frequently used in dermatology for cases treated with corticosteroids and/or immunosuppressants, it is often difficult to continue the administration of TMP/SMX due to adverse events. There are only a few reported studies on the prophylaxis of PCP in dermatology. This is the first review focused on adverse events of TMP/SMX among patients with dermatological diseases compared with previous reports. In this study, we retrospectively investigated 132 cases treated with TMP/SMX and examined the adverse events. Adverse events occurred in 32 cases (24.2%) and the incidence in this study was higher than in previous reports. Thrombocytopenia occurred in 17 cases (12.5%), which was the most frequent adverse event. The possible causes of adverse events were that the standard dose of TMP/SMX may be excessive for most Japanese, in addition to the long administration period, and the concomitant use of corticosteroids and/or immunosuppressants in almost all cases. We must consider the risks of PCP and adverse events of TMP/SMX in each case. It is desirable to examine possible administration methods that can be continued by adjusting the dose and interval of TMP/SMX.