Written by Adele Stapf, Helen Cooke, Helen Seers and the CAM-Cancer Consortium.
Updated February 8, 2017


Is it safe ?

Adverse events

When taken orally amygdalin or laetrile may result in serious adverse events. The intestinal microflora contains enzymes that enhance the release of cyanide in the intestinal tract.14

The adverse events observed reflect the symptoms of cyanide poisoning. Headache, dizziness, nausea and vomiting, dermatitis or, in severe cases, disturbed consciousness, tachycardia, respiratory distress, liver damage, coma and death may occur following oral administration. Several fatalities were attributed to drug preparations containing amygdalin.9 10

The risk of cyanide poisoning with oral intake of laetrile is increased when vitamin C is taken additionally.11 A case of adverse drug reaction showing signs and symptoms of a serious, life-threatening inadvertent cyanide poisoning has been reported in Australia in 2005. The report suggests that a female patient increased the cyanide toxicity risk by taking amygdalin concomitantly with a high dose of vitamin C (4,800 mg).12 A case report of a 4-year-old boy with severe encephalopathy due to cyanide poisoning after oral and intravenous administration of amygdalin has been published in 2015.13

Since the tolerance of amygdalin may vary greatly, it is impossible to predict the risk for an individual patient. A review concluded that there is a high risk of cyanide poisoning when amygdalin is taken orally.15

As opposed to oral administration, there is no proof for toxicities associated with parenterally administered pure amygdalin.  However, amygdalin preparations contaminated with beta-glucosidases, seen particularly when the product is made from apricot seeds, may enhance the hydrolysis of amygdalin and thus considerably increase its toxicity. In the presence of such contaminants even parenteral application of amygdalin may cause cyanide poisoning.4


In addition to the risks mentioned above, products containing amygdalin may decrease liver function in patients with hepatic impairment.10  The use of amygdalin during pregnancy or breast-feeding is contraindicated.


An experimental animal study showed no effect of amygdalin on the activity of the CYP2B isoenzymes; however there may be an effect on the subgroups CYP2A, 2C and 3A. There are no indications of any clinically relevant pharmacokinetic interactions.16


Particularly oral ingestion may result in a dose-dependent severe, possibly fatal cyanide poisoning.

Additionally, cases of mislabeling have been observed and investigations of samples showed contamination with bacteria, toxins and other substances.

Citation Adele Stapf, Helen Cooke, Helen Seers, CAM-Cancer Consortium. Amygdalin/Laetrile [online document]. http://ws.cam-cancer.org/The-Summaries/Dietary-approaches/Amygdalin-Laetrile. February 8, 2017.


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