The current status of laetrile.

Amygdalin at various concentrations and with numerous impurities is the most common cyanogenic glycoside found in laetrile samples. Its chemical properties were first described in 1837, and pharmacologic studies have shown that ultimately it is broken down to HCN, benzaldehyde, and glucose by enzymes found in gut bacteria but not intracellularly in humans. Fatal and nonfatal toxicities to orally ingested cyanogenic glycosides have been reported worldwide. We review here the signs and symptoms of acute cyanide toxicity and its treatment. Substantial in-vitro and in-vivo testing in animal tumor systems has shown that amygdalin is entirely devoid of significant anticancer activity. Control animals often have lived longer than those treated with various doses and schedules of amygdalin. Acceptable clinical studies in humans are lacking, but such ventures would appear to be contraindicated from animal studies and observed human toxicities. We also discuss current legal-judicial aspects of laetrile therapy for cancer.