Irreversible curarization.

The reversal effect of neostigmine following different doses of tubocurarine was investigated in 20 anesthetized adults. After five minutes, neostigmine could rapidly and effectively reverse a blocking dose of tubocurarine. Doubling the dose of tubocurarine necessitated a much higher concentration of neostigmine to achieve reversal, while a triple dose could be reversed only after enough time had elapsed to allow for lowering its concentration. It is concluded that the degree of reversal by neostigmine is related inversely to the concentration of tubocurarine at the time of reversal. An overdose of tubocurarine predisposes to the so called "neostigmine-resistant curarization".