Sulfamethoxazole
Sulfamethoxazole. Sulfonamide antibiotic — competitive inhibitor of bacterial dihydropteroate synthase (DHPS) blocking folate synthesis. Always… Oral half-life 14 h.
Sulfonamide antibiotic — competitive inhibitor of bacterial dihydropteroate synthase (DHPS) blocking folate synthesis. Always co-formulated with trimethoprim for synergistic folate-pathway blockade. CYP2C9 inhibitor (raises warfarin INR).
PK re-sourced to Chin 1995 (PMID:7695325), adult patients dosed intravenously then orally, sulfamethoxazole reported separately — verbatim "volume of distribution, ... 0.5 +/- 0.3 versus 0.4 +/- 0.1 liters/kg", "half-life, ... 15.5 +/- 9.5 versus 14.3 +/- 4.7 h" and "bioavailability was ... 86.2% +/- 17.9% versus 99.1% +/- 20.5% for sulfamethoxazole"; the non-critically-ill arm is stored. The previous citation described four children with biliary atresia and NO intravenous dosing though the IV row cited it. Two likely origins worth recording: the stored V of 14 L matches that paper sulfamethoxazole CLEARANCE of 13.7 mL/kg/h, and the stored F of 0.95 matches TRIMETHOPRIM fraction absorbed of 0.955 in a different paper.
Pharmacokinetics
- Oral — t½ 14.3 h · F 99% · Vd 28 L
- IV — t½ 14.3 h · F 100% · Vd 28 L
Sources: PMID:8696062, PMID:7695325