The Place of Erythroidines in the History of Neuromuscular Blockers.

Between 1938 and 1951 erythroidine derivatives were seriously considered as alternatives to curare for the provision of muscle relaxation. This has been overlooked in the published history of anaesthesia. The first publication on the paralysing effect of an extract of Erythrina americana was in 1877, but this was in a Mexican journal, which was not widely read. Sixty years later erythroidine was isolated, and in 1938 it was first used clinically to treat spastic dystonia, preceding the use of Intocostrin for this purpose. By 1943 dihydro-β-erythroidine was prepared in crystalline form, which was equipotent with curarine and of acceptable duration; it was used in clinical anaesthesia in 1946. In the 1940s curare was presented in solutions with potency stated in units, determined by bioassay, which was a disadvantage compared with the straightforward mg of dihydro-β-erythroidine. However, by the early 1950s, improvement in the pharmaceutical presentation of d-tubocurarine and new neuromuscular blockers, displaced the erythroidines.