neosaxitoxin + epinephrine

Neosaxitoxin + epinephrine is an investigational combination drug for prolonged local anesthesia. Neosaxitoxin is a site-1 sodium channel blocker, belonging to a group of paralytic shellfish toxins, that produces a long-lasting nerve block by inhibiting action potential propagation along nerves. When combined with epinephrine, a potent vasoconstrictor and sympathomimetic agent acting on alpha- and beta-adrenergic receptors, the anesthetic effect of neosaxitoxin is substantially potentiated: epinephrine decreases systemic toxicity, increases the safety margin, reduces local blood flow to delay systemic absorption, and further prolongs the duration of anesthesia. This combination has been studied in animal models and in randomized controlled trials in humans, showing significant extension of analgesic duration and reduction of side effects compared to neosaxitoxin alone[1][3][5].