Interaction between chioramphenicol and acetaminophen

Acetaminophen has been reported either to prolong or not to affect the clearance of chioramphenicol. To confirm one of these findings we studied the clearance of chloramphenicol and its metabolites using high pressure liquid chromatography in five patients (ages 2·5 to 5 years) before and during oral treatment with acetaminophen (50 mg/kg/day). Significant differences were observed in mean (SD) peak serum chioramphenicol concentration (-97 (3.2) mg/I), mean (SD) apparent volume of distribution (+225 (162) mI/kg), mean (SD) chioramphenicol half life (-1.9 (1.1) hours), mean (SD) chioramphenicol clearance (+236 (94) mL/kg/h), mean (SD) area under the curve (-83·5 (33.0) mg/I/h), and mean (SD) elimination constant (+0.34 (O·13)h ¹) between samples obtained before and during treatment with acetaminophen. Acetaminophen, when given orally for several days, increased the clearance of chloramphenicol, perhaps by increased glucuronidation. This report re-emphasises the need for therapeutic drug monitoring whenever these two drugs are used together.