Subcutaneous brompheniramine for cutaneous analgesia in rats

Brompheniramine as an antihistamine blocked sodium channels, and local anesthetics by blocking sodium channels produced the local anesthetic effects. The authors aimed to assess local anesthetic quality and duration of brompheniramine when compared to the local anesthetic mepivacaine. After rats were shaved and injected subcutaneously on the dorsal skin, the panniculus reflex, induced via applying a noxious pinprick to the skin (injected area), was scored. The dose-response curve and nociceptive block duration of brompheniramine were constructed and compared with mepivacaine. The cutaneous analgesic effects in both brompheniramine and mepivacaine groups were concentration-dependent. On the basis of the amount required to produce a 50% block effect (ED₅₀, 50% effective dose), the drug's potency was brompheniramine (0.89 [0.82-0.96] μmol) better than mepivacaine (2.45 [2.17-2.76] μmol) (P < 0.01). Full recovery time of brompheniramine was more prolonged than mepivacaine's (P < 0.01) on infiltrative cutaneous analgesia when comparing ED₂₅s, ED₅₀s and ED₇₅s. Our preclinical data demonstrated that subcutaneous brompheniramine induces dose-relatedly analgesic effects, and brompheniramine induces prolonged analgesic duration when compared with mepivacaine. Brompheniramine also provokes better cutaneous analgesia than mepivacaine.