Pharmacokinetics of sulfamethoxazole and trimethoprim during veno‐venous extracorporeal membrane oxygenation: A case report

: Extra-corporeal membrane oxygenation (ECMO) therapy could affect drug concentrations via adsorption onto the oxygenator and/or associated circuit. We describe a case of a 33-year old male with severe respiratory failure due to Pneumocystis jirovecii infection on a background of recently diagnosed HIV infection. He required veno-venous ECMO therapy for refractory respiratory failure. Intravenous sulfamethoxazole-trimethoprim (100 mg/kg/day and 20 mg/kg/day) was administered in a 6-hourly dosing regimen. Pre-oxygenator, post-oxygenator and arterial blood samples were collected post antibiotic administration and were analyzed for total sulfamethoxazole and trimethoprim concentrations. The peak sulfamethoxazole and trimethoprim concentrations were 122 mg/L and 5.3 mg/L, respectively. The volume of distribution for sulfamethoxazole was 0.37 L/kg and 2.30 L/Kg for trimethoprim. The clearance for sulfamethoxazole was 0.35 ml/min/kg and for trimethoprim was 1.64 mL/min/kg. The pharmacokinetics of sulfamethoxazole and trimethoprim appear not to be affected by ECMO therapy and dosing adjustment may not be required.