Skin nociceptive block with pramoxine delivery by subcutaneous injection in rats

Background: Pramoxine has been shown to produce spinal anesthesia, while cutaneous analgesia (peripheral) of pramoxine is not established. The experimental goal was to examine cutaneous antinociception produced by a local anesthetic (LA) pramoxine and compare this result with that of another well-known LA lidocaine. Methods: Cutaneous antinociception was evaluated by blockade of pinprick- induced cutaneous trunci muscle reflex (CTMR) on the skin of rat's back. After the dose–related curves were constructed, the quality and duration of drug's (lidocaine and pramoxine) cutaneous antinociception were compared. Results: We showed that pramoxine, as well as lidocaine produced skin antinociception in a dose–related fashion. The relative potency (ED₅₀ [50% effective dose] basis) was lidocaine (5.44 [4.67–6.35] μmol) greater than pramoxine (42.1 [38.8–45.7] μmol) (p < 0.01). On the basis of equianalgesic doses (ED₇₅, ED₅₀, and ED₂₅), pramoxine caused equivalent duration of cutaneous antinociception to lidocaine. Conclusions: These preclinical data indicated that pramoxine elicits skin antinociception dose-relatedly. Pramoxine exhibits a potency less than that of lidocaine while they have a comparable duration of skin antinociceptive action.