Dental impaction pain model as a potential tool to evaluate drugs with efficacy in neuropathic pain.

Intravenous lidocaine, a nonspecific Na-channel blocker, was used to assess the dental impaction model for evaluation of neuropathic pain drugs. Sixty patients, experiencing moderate or severe pain after removal of > or = 2 third molars, were randomized (2:2:1:1) to lidocaine (4 mg/kg; maximal dose 300 mg), oxycodone/acetaminophen (10/650 mg), placebo, and active placebo (diphenhydramine, 50 mg). Lidocaine provided a modest degree of pain relief. Predefined endpoints of total pain relief and sum of pain intensity at 2, 4, and 6 hours showed numerically, not statistically significantly, greater pain relief versus placebo. A significantly greater effect over placebo was observed in peak effect and at shorter time points (30 minutes and 1 hour), consistent with the pharmacokinetic profile (plasma concentration of approximately 2 mug/mL). Oxycodone/acetaminophen provided significantly greater analgesia versus placebo, validating study conduct, and significantly greater pain relief was observed versus lidocaine, which is consistent with a smaller portion of dental extraction pain being of neuropathic origin.