Pharmacokinetics and metabolism of naproxen in children

The metabolism and pharmacokinetics of orally administered naproxen were studied in 10 children aged 6-13 years. 3 patients received the drug for antipyresis and 7 for postoperative pain. The mean elimination rate constant was greater in the febrile children than the postoperative patients, 0.064 h-1 vs. 0.051 h-1. 71% of total drug recovered in urine was naproxen, and 29% was excreted as the desmethyl metabolite. 60 and 63% of naproxen and desmethyl naproxen, respectively, were excreted as conjugates. Area under the curve and fraction of dose recovered in the urine were reduced in the postoperative patients, suggesting reduced gastrointestinal absorption of the drug compared to the febrile patients.