Evaluation of effectiveness, hyperkalaemia, and hepatotoxicity of trimethoprim-sulphamethoxazole prophylaxis for Pneumocystis jirovecii pneumonia in paediatric patients: A single-centre retrospective study

American guidelines recommend trimethoprim-sulfamethoxazole (TMP-SMX) for preventing Pneumocystis jirovecii pneumonia (PJP) in pediatric patients at doses of 5–10 mg/kg/day of the TMP component, administered either daily, three times weekly, or twice weekly. However, limited studies describe the effectiveness and safety of these prophylactic regimens. Our study aimed to assess the clinical effectiveness and incidence of adverse events associated with each TMP-SMX regimen in pediatric patients, and to identify risk factors for adverse events. We collected data regarding the onset of PJP, hyperkalemia, and hepatotoxicity in patients aged 0–18 years who underwent prophylaxis with TMP-SMX from July 2018 to June 2023. A total of 215 pediatric patients met the inclusion criteria. No patients developed PJP. Hyperkalemia occurred in 14.7%, patients receiving TMP-SMX daily, 15.4% receiving it three times weekly, and 15.5% receiving it twice weekly. Hepatotoxicity was most frequent in patients receiving TMP-SMX twice weekly (19.0%), followed by those receiving it three times weekly (7.7%), and daily (5.9%). Younger patients were significantly more prone to developing hyperkalemia or hepatotoxicity. Patients aged <1 year had the highest incidences of hyperkalemia (56.5%), and those aged 1–2 years had the highest incidence of hepatotoxicity (25.0%). No patient developed PJP under various dosage prophylactic regimens of TMP-SMX. However, our findings suggest the need to monitor potassium levels and hepatic function in patients undergoing any of the three TMP-SMX regimens. In particular, patients aged <1 year old and 1-2 years old face a higher risk of hyperkalemia and hepatotoxicity, respectively.