A human oral capsaicin pain model to assess topical anesthetic-analgesic drugs.

Repeated application of capsaicin on the tongue has been used as a human oral pain model to assess topical anesthetic-analgesic drugs. The reliability of the model was evaluated by observing the variability of the response to repeated applications of capsaicin after three successive sessions at 1 day intervals. No session effect was observed for the time course of the visual analogue scale (VAS) scores and the area under the curve, but a significant decrease of VAS peak scores was noted from the first to the third session. The sensitivity of the model was assessed by mouth rinses with three doses of lidocaine (0.25, 0.5 and 1%). Lidocaine significantly reduced the burning pain. This effect was rapid, reversible and dose dependent. It is concluded that the oral capsaicin pain model displays good reliability and sensitivity and allows safe evaluation of candidate topical analgesic and anesthetic drugs.