Ibuprofen is a safe and effective analgesic, but some formulations have a slow onset of action. Ibuprofen arginate is a rapidly absorbed salt designed to promote more rapid onset of analgesia. A clinical trial was conducted in 226 patients with postoperative dental pain to assess the analgesic efficacy and speed of onset of the arginine salt of ibuprofen compared with one of the commercially available forms of ibuprofen. Patients were administered a single dose of either ibuprofen arginate (200 mg or 400 mg), ibuprofen (200 mg or 400 mg), or placebo in this double-blind, randomized trial. To determine the onset of action of the study medication patients were required to note time to "any" pain relief and then time to "meaningful" pain relief, using the two-stopwatch method. Pain intensity and relief were assessed using traditional categorical scales over a 6-h period. Meaningful pain relief was achieved in 42 min and 24 min for ibuprofen arginate 200 mg and 400 mg, respectively, compared with 50 min and 48 min for ibuprofen 200 mg and 400 mg, respectively ( P<0.05). The results for the measurements of analgesic effectiveness [sum of pain intensity difference, total pain relief (TOTPAR), peak pain relief and overall evaluation of treatment] all showed that both doses of ibuprofen arginate and both doses of ibuprofen were significantly better than placebo and both 200-mg and 400-mg ibuprofen arginate doses were significantly better than ibuprofen 200 mg for peak pain relief. Mean plasma ibuprofen concentrations at 30 min and 60 min, respectively, were: ibuprofen arginine 200 mg, 13.9 micro g/ml and 15.7 micro g/ml; ibuprofen arginine 400 mg, 29.5 micro g/ml and 29.3 micro g/ml; ibuprofen 200 mg 2.5 micro g/ml and 5 micro g/ml; ibuprofen 400 mg, 2.3 micro g/ml and 7.4 micro g/ml. ( P<0.05). Adverse event profiles were similar across treatment groups. These results overall suggest that ibuprofen arginate when taken at doses equivalent to commercially available ibuprofen formulations produces analgesia that is faster in onset.