Co-trimoxazole desensitization in HIV-seropositive patients

Co-trimoxazole (trimethoprim-sulphamethoxazole) is an effective prophylactic agent against Pneumocystis carinii pneumonia (PCP). However, it is associated with a high frequency of adverse reactions in immunocompromised patients which may preclude its use. Fourteen patients with a definite history of adverse reactions to co-trimoxazole on standard PCP prophylactic dosage were selected for desensitization using a regimen of gradual incremental exposure over an 11-day period. Eight (57.1%) were successfully desensitized and have continued on oral co-trimoxazole at maximum 21 months' follow-up. This report demonstrates that oral desensitization as an outpatient procedure is an effective and safe option for both primary and secondary PCP prophylaxis in HIV-seropositive patients with previous adverse drug reactions.