Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection that adversely affects solid organ transplant (SOT) recipients. Published guidelines endorse 5 to 10 mg/kg/day (trimethoprim component) trimethoprim-sulfamethoxazole (TMP-SMX) as the recommended regimen for PJP prevention, often resulting in drug-related adverse effects. We investigated the use of a low-dose TMP-SMX regimen given at 2.5 mg/kg/dose once daily every Monday, Wednesday, and Friday at a large pediatric transplantation center.


A retrospective chart review was conducted, including patients ages 0 to 21 years who underwent SOT from January 1, 2012, to May 1, 2020, and who were subsequently started on PJP prophylaxis with low-dose TMP-SMX for a minimum of 6 months. The primary end point was the incidence of breakthrough PJP infection on the low-dose TMP-SMX regimen. Secondary end points include the prevalence of adverse effects characteristic of TMP-SMX.


A total of 234 patients were included in this study, and 6 of 234 patients (2.6%) were empirically transitioned to treatment dosing of TMP-SMX given a clinical concern for PJP, although none received a diagnosis of PJP. There were 7 patients (2.6%) who experienced hyperkalemia, 36 (13.3%) had neutropenia, and 22 (8.1%) had thrombocytopenia (all grade 4). Clinically significant serum creatinine elevations were seen in 43 of 271 patients (15.9%). Elevations of liver enzymes were seen in 16 of 271 patients (5.9%). Rash was documented in 4 of 271 patients (1.5%).


In our patient cohort, low-dose TMP-SMX preserves the efficacy of PJP prophylaxis while providing an acceptable adverse effect profile.

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