Evaluation of onset of pain relief from micronized aspirin in a dental pain model.

A new formulation of a micronized acetylsalicylic acid swallowable tablet with an effervescent component (FR-aspirin) was evaluated in two independent studies using the dental impaction pain model. These clinical studies were performed to confirm the results of preclinical dissolution studies and human pharmacokinetic studies, which indicated an improved onset of analgesia without compromising duration of effect or safety. Study 1 evaluated a 650-mg dose of aspirin and Study 2 evaluated a 1,000-mg dose of aspirin. Both studies were double-blinded, parallel group and compared to regular aspirin (R-aspirin) and placebo. Speed of onset was measured by the double stopwatch method for time to both first perceptible relief and meaningful relief. In both studies, the FR-aspirin was significantly faster (p<0.038-0.001) than both R-aspirin and placebo for both onset measures. There were no significant differences between FR-aspirin and R-aspirin for peak or total effects and both treatments were significantly better than placebo. For first perceptible relief, FR-aspirin onset was 19.8 and 16.3 min for 650 mg and 1,000 mg, respectively, compared to 23.7 and 20.0 for R-aspirin. For meaningful relief, FR-aspirin onset was 48.9 and 49.4 min for 650 mg and 1,000 mg, respectively, compared to 119.2 and 99.2 for R-aspirin. These efficacy studies clearly demonstrate that the onset of analgesic efficacy is dramatically improved by adding an effervescent component and micronized active ingredient to the swallowable tablet aspirin formulation. The enhanced onset did not adversely impact either the peak effect or duration of effect or tolerability compared to regular aspirin.