Is it safe ?
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.
CitationAdele Stapf, Helen Cooke, Helen Seers, CAM-Cancer Consortium. Amygdalin/Laetrile [online document]. http://www.cam-cancer.org/CAM-Summaries/Dietary-approaches/Amygdalin-Laetrile. July 20, 2015.
Updated and revised in July 2015 by Adele Stapf.
Updated in April 2014 by Barbara Wider.
Assessed as up to date in December 2012 by Helen Cooke.
Most recent update and revision in December 2011 by Helen Cooke.
Fully revised and updated in July 2009 by Helen Cooke.
Summary first published in September 2005, authored by Helen Seers.
- Davignon, JP, Trissel, LA, & Kleinman, LM. Pharmaceutical assessment of amygdalin (Laetrile) products. Cancer Treatment Reports. 1978; 62 (1): 99-104.
- Chandler, RF, Phillipson, JD & Anderson, LA. Controversial Laetrile. Journal of Pharmacology. 1984; 232: 330-332
- Ellison, NM, Byar, DP, & Newell, GR. Special report on Laetrile: the NCI Laetrile Review. Results of the National Cancer Institute's retrospective Laetrile analysis.New England Journal of Medicine. 1978; 7;299 (10):549-52.
- Bulletin zur Arzneimittelsicherheit. Informationen aus BfArM und PEI. Ausgabe 3, September 2014. http://www.bfarm.de/bulletin
- McCarrison, SR. “Nutrition and National Health.” Journal of the Royal Society of Arts. 1936. lxxxiv, 1047, 1067, 1087.
- Milazzo S & Horneber M. Laetrile treatment for cancer. Cochrane Database Syst Rev. 2015 Apr 28;4:CD005476. doi: 0.1002/14651858.CD005476.pub4.
- Moertel, CG, Ames, MM, Kovach, JS, et al. A pharmacologic and toxicological study of amygdalin. Journal of the American Medical Association. 1981. 245 (6): 591-4.
- Moertel, CG, Fleming, TR, Rubin, J, et al. A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. New England Journal of Medicine. 1982; 306 (4): 201-6.
- Braico, KT, Humbert, JR, Terplan, KL, & Lehotay, JM. Laetrile intoxication: report of a fatal case, New England Journal of Medicine. 1979; 1; 300 (5): 238-40.
- Sadoff, L, Fuchs, K, & Hollander, J, Rapid death associated with Laetrile ingestion, Journal of the American Medical Association. 1978; 14; 239 (15): 1532.
- Lee, M, Berger, HW, Givre, HL, et al. Near fatal Laetrile intoxication: Complete recovery with supportive treatment, Mount Sinai Journal of Medicine. 1982; 49 (4): 305-307.
- Bromley J, Hughes BG, Leong DC, Buckley NA. Life-threatening interaction between complementary medicines: cyanide toxicity following ingestion of amygdalin and vitamin C. Ann Pharmacother. 2005 Sep;39(9):1566-9.
- Sauer H, Wollny C, Oster I, Tutdibi E, Gortner L, Gottschling S, Meyer S. Severe cyanide poisoning from an alternative medicine treatment with amygdalin and apricot kernels in a 4-year-old child. Wien Med Wochenschr. 2015 May;165(9-10):185-188.
- Newmark J, Brady, RO, Grimley, PM, Gal, AE, Waller, SG, & Thistlethwaite, JR. Amygdalin (Laetrile) and pruasin beta-glucosidases: Distribution in germ free rat and in human tumor tissue. Proceedings of the National Academy of Sciences of the United States of America. 1981; 78 (10): 6513-6.
- Milazzo S, Lejeune S, Ernst E. Laetrile for cancer: a systematic review of the clinical evidence. Support Care Cancer. 2007 Jun;15(6):583-95.
- Yamada H, Nakamura T, Oguri K. Induction of rat hepatic cytochromes P450 by toxic ingredients in plants: lack of correlation between toxicity and inductive activity. J Toxicol Sci. 1998 Dec;23(5):395-402.
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