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 (ED ₅₀ [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 (ED ₇₅ , ED ₅₀ , and ED ₂₅ ), 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.
(Copyright © 2018 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.)