A DOUBLE-BLIND, PLACEBO CONTROLLED, CROSS-OVER COMPARISON OF THE ANALGESIC EFFECT OF IBUPROFEN 400 MG AND 800 MG ON LASER-INDUCED PAIN

1. The analgesic efficacy of single oral doses (400 mg, 800 mg) of ibuprofen on argon laser-induced pain was studied in a double-blind, placebo controlled, three way cross-over comparison. Ten healthy volunteers participated. 2. Pain thresholds and plasma concentrations of the S- and R-enantiomers of ibuprofen were measured every hour up to 8 h after medication. 3. Ibuprofen (400 mg) produced an analgesic effect significantly superior (P < 0.05) to placebo 1-4 h after medication. Ibuprofen (800 mg) was significantly superior to placebo 2-4 h after administration. No differences were found between 400 mg and 800 mg, when hourly threshold differences were compared. 4 Comparing total analgesic effect (area under effect curve), both active medications were superior to placebo (P < 0.01-0.05), and 400 mg was superior to 800 mg (P < 0.05). 5 Peak plasma concentrations of S- and R-ibuprofen occurred between 1.2 and 1.5 h. Concentrations after the 800 mg dose were higher than those after the 400 mg dose at all times.