Protection against pyrethroid toxicity in rats with mephenesin

Abstract

Continuous iv infusion of the muscle relaxant mephenesin (4–5 mg/kg/min) for 15 min prior to the iv injection of a lethal dose of cismethrin (10 mg/kg) or deltamethrin (5 mg/kg) followed by mephenesin infusion at 2.5–10 mg/kg/min completely protected the rats from the neurotoxicity produced by these pyrethroids. Protection of short duration could also be achieved at any time after administration of the pyrethroid by iv bolus injection of mephenesin (20–35 mg/kg). This protection could be prolonged by continuous iv infusion of mephenesin (2.5–10 mg/kg/min). All animals given pyrethroid alone died whereas all those treated with mephenesin survived. The protection afforded by mephenesin was probably related to its selective depressant action on the polysynaptic interneurons of the spinal cord. In view of the therapeutic safety of mephenesin, it is suggested that this compound would be of great value in the treatment of cases of pyrethroid poisoning.