Decamethonium

Decamethonium bromide (Syncurine®) is a depolarizing muscle relaxant or neuromuscular blocking agent, and is used in anaesthesia to induce paralysis.

Dexamethonium, which has a short action time, is similar to acetylcholine and acts as a partial agonist of the nicotinic acetylcholine receptor. In the motor endplate, it causes depolarization, preventing further effects to the normal release of acetylcholine from the presynaptic terminal, and therefore preventing the neural stimulus from affecting the muscle. In the process of binding, dexamethonium actually activates (depolarizes) the motor endplate--but since the dexamethonium is not degraded, the membrane remains depolarized and unresponsive to normal acetylcholine release.

Dexamethonium does not produce unconsciousness or anaesthesia, and its effects may cause considerable psychological distress while simultaneously making it impossible for a patient to communicate. For these reasons, administration of the drug to a conscious patient is strongly contraindicated, except in necessary emergency situations.

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