On the Effect of a Muscle Relaxing Compound, Succinylcholine

　Succinyl-bis-choline (Subch) is now used in therapy as a short-acting curare-like muscle relaxant. Succinylmono-choline (Sumch) has a similar effect to Subch but is far less effective, i. e.，about one-tenth of Subch. The short time effect of Subch is ordinarily explained as a result of its rapid splitting by cholinesterase (2, 3).

　The splitting of Subch in vitro, however, is not so rapid as would be expected from the in vivo effect (4-6). 0.5 ml serum, which could split 1 mg ACh within 15 minutes, split only 10 to 20 per cent of 1 mg Subch in 6 hours, and even after 24 hours there remained a significant amount of the drug.