How It Works
Bottom Line: Amygdalin (Laetrile) does NOT work. It often has toxic side effects and has caused decreased survival in cancer patients.
Amygdalin (also called Laetrile®) is an extract from apricot pits that can be metabolized to cyanide, a known poison. It was first used in the 1920s and was promoted widely in the 1950s as a cancer therapy. Promoters claimed that the cyanide released from amygdalin selectively killed cancer cells, leaving normal tissue cells alone. This theory has been proven false by laboratory experiments that showed that amygdalin, when fed to laboratory animals that had cancer cells implanted in them, was not able to reduce the size or slow the growth of their tumors. This was true for many different types of cancer cells. Cyanide does kill cells in laboratory experiments, but affects all cells (both cancerous and healthy) in the same way, which explains the handful of cyanide poisonings that have been reported in cancer patients using amygdalin/Laetrile®.
Purported Uses
To prevent and treat cancer
Laboratory and clinical evidence does not support this use. In fact, amygdalin (Laetrile®) has been linked to several cases of cyanide poisoning in cancer patients.
Research Evidence
Cancer treatment:
In 1982, a clinical trial in the New England Journal of Medicine evaluated amygdalin as part of a metabolic therapy for treating cancer. One hundred and seventy-eight patients with various cancers volunteered to take part in the study; they received 4.5 grams/m2 of intravenous amygdalin for 21 days, followed by 500 mg of amygdalin in tablets three times a day. The metabolic therapy also consisted of vitamins, minerals, a pancreatic enzyme supplement, and a restricted diet. 79% of the patients had tumor growth after two months, and 91% by three months. The average survival was about five months, and many cases of cyanide poisoning were found. These results are quite poor compared to typical survival in patients using conventional cancer treatments, and they strongly suggest that amygdalin is ineffective in treating cancer.
Warnings
Amygdalin is not an approved drug in the United States.
Laboratory analysis showed that some samples of amygdalin have been contaminated with microbes and pyrogens (substances that induce fever). This analysis also showed that both the injectable and oral dosage forms contained less active product than was claimed on the label.
Do Not Take If
Side Effects
Dermatitis (rashy inflammation and redness of the skin)
Cyanide toxicity from high doses or prolonged use of amygdalin can cause nausea, vomiting, headaches, dizziness, mental confusion, cyanosis (bluish discoloration of the skin), low blood pressure, ptosis (drooping of the eyelids), nerve dysfunction, coma, and death.
Special Point
The Food and Drug Administration has banned the sale and use of amygdalin (Laetrile®) due to the risk of cyanide poisoning. For this reason, Laetrile® is only offered at alternative medicine clinics in Tijuana, Mexico as a component of multi-modality metabolic therapies. Such therapies generally have not been found effective and are discussed at greater length in a separate mongraph about
metabolic therapies.
Scientific Name
D-mandelonitrile-b-D-glucosido-6-b-D-glucoside
Common Name
Apricot pits, vitamin B17, mandelonitrile-beta-glucuronide (semi-synthetic), mandelonitrile beta-D-gentiobioside (natural product), laevorotatory and mandelonitrile, prunasin
Brand Name
Laetrile®, Amigdalina
Clinical Summary
A naturally occurring cyanogenic glycoside derived from nuts, plants, and the pits of certain fruits, primarily apricots. It was first used in Russia in 1845 and later, in the United States, in the 1920s as a cancer treatment. It become popular once again in the 1970s in Mexico. Although patients use amygdalin, commonly called laetrile, research has demonstrated only the absence of beneficial effect (3). Amygdalin is metabolized by beta-glucosidase to cyanide, benzaldehyde, and prunasin (1). Oral administration has resulted in cyanide toxicity and death (4) (6) (7). According to a recent case report, ingestion of 3 grams of amygdalin with concurrent use of high doses of vitamin C led to severe cyanide poisoning (9). Amygdalin is not an approved drug in the United States, but is available in some foreign clinics and via the Internet. Pharmaceutical evaluation of the parenteral formulation showed contamination with both pyrogens and microbes, and both oral and parenteral formulations did not contain labeled amounts of amygdalin (5). Patients should not use this supplement.
Purported uses
- Cancer prevention
- Cancer treatment
Constituents
D-mandelonitrile-b-D-glucosido-6-b-D-glucoside
Mechanism of Action
The mechanism of action is unknown. Claims for amygdalin's activity rely on the theory, now proven false, that cancer cells contain elevated amounts of beta-glucosidase and reduced levels of rhodanese compared to normal cells
(1) (2). Based on this incorrect assumption, cancer cells were claimed to metabolize amygdalin into cyanide and die, while healthy cells would convert cyanide to benign thiocyanate via rhodanese. Limited in vitro data support the idea that cyanide, benzaldehyde, and prunasin are cytotoxic. It has also been postulated that cancer develops due to deficiencies in vitamin B17, but no data substantiate this idea
(8).
Pharmacokinetics
Hydrocyanic acid, or cyanide, and benzaldehyde are formed from mandelonitrile when amygdalin is metabolized by beta-glucosidase enzymes in the cell. Administration of amygdalin 4.5 grams/m
2 intravenously to cancer patients displays two-compartment open model kinetics. Elimination half-life is approximately 2 hours with a mean clearance of 99 ml/min. No changes in whole blood levels of cyanide or thiocyanate were noted with parenteral administration
(4). Repeated oral administration of amygdalin 500 mg tablets in cancer patients resulted in increased whole blood cyanide levels of averaging approximately 1 mcg/ml (range 0-3 mcg/ml)
(2).
Warnings
Amygdalin is not approved for use in the United States.
Pharmaceutical evaluation of the injectable formulation showed pyrogen and microbial contamination, and both injectable and oral dosage forms did not contain labeled amount of amygdalin.
(5)
Adverse Reactions
Reported (oral): Dermatitis and cyanide toxicity consisting of nausea, vomiting, headache, dizziness, mental obtundation, cyanosis, hypotension, ptosis, neuropathies, coma, and death.
(3) (6) (7)Reported (oral): Severe cyanide poisoning following ingestion of 3 grams of amygdalin with concurrent use of high doses of vitamin C.
(9)
Herb-Drug Interactions
Ascorbic acid: Ascorbic acid may increase the toxicity of amygdalin.
Food: Beta-glucosidase is found in certain foods (e.g. almonds, celery, peaches, carrots) and may increase the toxicity of amygdalin.
Lab Interactions
Increased temperature
Reduce oxygen saturation
Literature Summary and Critique
Moertel CG, et al. A clinical trial of amygdalin (laetrile) in the treatment of human cancer. New Eng J Med 1982;306:201-6. A prospective, open-label evaluation of amygdalin plus "metabolic therapy" on 178 patients with various cancers. All patients were in generally good health and a third had not received any prior treatment. Patients received 21 days of intravenous amygdalin 4.5 grams/m
2 followed by 500 mg amygdalin tablets three times a day. In addition, patients were placed on a metabolic therapy consisting of vitamins (A, C, E, B complex), minerals, and pancreatic enzyme supplementation. A diet restricting eggs, dairy, meats, and caffeinated and alcoholic beverages was also encouraged. Primary outcomes measured were tumor response and survival. Of the 175 evaluable patients, there was one partial response, 79% had progression of disease after two months and 91% by three months. Median survival based on all patients was 4.8 months from initiation of therapy. Many adverse effects noted were related to cyanide toxicity, including headache, nausea, vomiting, dizziness, and mental obtundation. The results suggest that amygdalin is ineffective in the treatment of cancer.
References
- Newmark J, et al. Amygdalin (laetrile) and prunasin beta-glucosidases: distribution in germ-free rat and in human tumor tissue. Proc Natl Acad Sci USA 1981;78:6513-6.
- Ames MM, et al. Pharmacology of amygdalin (laetrile) in cancer patients. Cancer Chemother Pharmacol 1981;6:51-7.
- Moertel CG, et al. A clinical trial of amygdalin (laetrile) in the treatment of human cancer. New Eng J Med 1982;306:201-6.
- Moertel CG, et al. A pharmacologic and toxicological study of amygdalin. JAMA 1981;245:561-4.
- Davignon JP, Trissel LA, Kleinman LM. Pharmaceutical assessment of amygdalin (laetrile) products. Cancer Treat Rep 1978;62:99-104.
- Sadoff L, Fuchs K, Hollander J. Rapid death associated with laetrile ingestion. JAMA 1978;239:1532.
- Kalyanaraman UP, et al. Neuromyopathy of cyanide intoxication due to "laetrile" (amygdalin). Cancer 1983;51:2126-33.
- Greenberg D. The case against laetrile: the fraudulent cancer remedy. Cancer. 1980 Feb 15;45(4):799-807.
- Bromley J, et al. LIfe-Threatening interaction between complementary medicines: Cyanide toxicity following ingestion of amygdalin and vitamin C. Ann Pharmacother 2005.
