Analgesic efficacy of acetaminophen sustained release.

The analgesic efficacy of acetaminophen sustained release (SR) and acetaminophen immediate plus sustained release (IR + SR) was evaluated in 200 outpatients with pain after oral surgery. Under double-blind conditions SR high dose (2000 mg) or low dose (1000 mg), IR + SR high dose (500 + 1500 mg) or low dose (250 + 750 mg), or acetaminophen standard tablet high dose (1000 mg) or low dose (500 mg) were randomly administered after removal of a lower third molar. The hourly pain intensity was rated on a visual analog scale during 12 hours. The efficacy was based on peak effect (maximum pain intensity difference in percent), pain reduction (mean percentage pain intensity difference), duration of effect (time to remedication) and pain reduction index (pain reduction multiplied by duration of effect). Pain reduction was 37% with the 500-mg tablet and 54% with SR 2000 mg. The peak effect increased from 53% after 1.9 hours for the 500-mg tablet to 67% after 2.6 hours for SR 2000 mg. The SR formulation significantly increased the duration of effect without reduction in peak effect.