MODE OF ACTION OF DEPOLARIZING AGENTS

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Abstract
SUMMARY: It has been shown that with suitable doses of decamethonium, succinylcholine, or succinylmonocholine, a two‐phase neuromuscular block can always be seen in isolated human intercostal muscle.The first phase consists of a neuromuscular block of rapid onset which reaches a maximum in about 15 minutes and then recovers spontaneously in spite of the continued presence of C10in the same concentration. Recovery is maximum at approximately 60 minutes, after which time the second phase begins.The second phase consists of a slow, progressive neuromuscular block which reaches a steady reproducible state after 6 to 8 hours. If undisturbed, this state remains constant for hours. This phase represents a true competitive neuromuscular block, as evidenced by the fact that it can be reversed by a suitable dose of neostigmine.Experiments have been described in which these two phases were modified by the addition of d‐tubocurarine and neostigmine. Attempts are made to explain various phenomena on a molecular basis. The clinical significance of this work is presented.