Analgesic properties of lidocaine in mice

The analgesic properties of lidocaine and morphine were compared in mice using a hot plate stimulus. An analgesic response was defined as an increase in the time required for an animal to attempt to escape by jumping. When compared to saline-treated controls, lidocaine produced a statistically significant dose-related delay in response to heat. Dose-response curves for morphine and lidocaine indicated that morphine has greater potency and efficacy. Naloxone (1.0 mg/kg) reversed the analgesic response due to morphine (10 mg/kg) but had no effect on the analgesia produced by lidocaine (50 mg/kg).