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Laetrile/Amygdalin (PDQ®)

Adverse Effects

The side effects associated with laetrile treatment mirror the symptoms of cyanide poisoning. Cyanide is a neurotoxin that can cause nausea and vomiting, headache,[1] dizziness,[2,3] cyanosis (bluish discoloration of the skin resulting from oxygen-deprived hemoglobin in the blood), liver damage,[4,5] hypotension (abnormally low blood pressure),[1,6,7] ptosis (droopy upper eyelid),[8,9] ataxic neuropathies (difficulty walking caused by damaged nerves),[10] fever,[7,8] mental confusion, coma, and death.[6,11-13] Oral laetrile causes more severe side effects than injected laetrile. These side effects can be potentiated (increased) by the concurrent administration of raw almonds or crushed fruit pits, and by eating fruits or vegetables that contain beta-glucosidase (e.g., celery, peaches, bean sprouts, carrots),[3,5,14-16] or by taking high doses of vitamin C orally.[1,5,17,18]


  1. Howard-Ruben J, Miller NJ: Unproven methods of cancer management. Part II: Current trends and implications for patient care. Oncol Nurs Forum 11 (1): 67-73, 1984 Jan-Feb. [PUBMED Abstract]
  2. Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982. [PUBMED Abstract]
  3. Chandler RF, Anderson LA, Phillipson JD: Laetrile in perspective. Can Pharm J 117 (11): 517-20, 1984.
  4. Leor R, Michaeli J, Brezis M, et al.: Laetrile intoxication and hepatic necrosis: a possible association. South Med J 79 (2): 259-60, 1986. [PUBMED Abstract]
  5. Lee M, Berger HW, Givre HL, et al.: Near fatal laetrile intoxication: complete recovery with supportive treatment. Mt Sinai J Med 49 (4): 305-7, 1982 Jul-Aug. [PUBMED Abstract]
  6. Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.
  7. Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978. [PUBMED Abstract]
  8. Smith FP, Butler TP, Cohan S, et al.: Laetrile toxicity: a report of two patients. Cancer Treat Rep 62 (1): 169-71, 1978. [PUBMED Abstract]
  9. Vizel M, Oster MW: Ocular side effects of cancer chemotherapy. Cancer 49 (10): 1999-2002, 1982. [PUBMED Abstract]
  10. Kalyanaraman UP, Kalyanaraman K, Cullinan SA, et al.: Neuromyopathy of cyanide intoxication due to "laetrile" (amygdalin). A clinicopathologic study. Cancer 51 (11): 2126-33, 1983. [PUBMED Abstract]
  11. Ames MM, Moyer TP, Kovach JS, et al.: Pharmacology of amygdalin (laetrile) in cancer patients. Cancer Chemother Pharmacol 6 (1): 51-7, 1981. [PUBMED Abstract]
  12. Moertel CG, Ames MM, Kovach JS, et al.: A pharmacologic and toxicological study of amygdalin. JAMA 245 (6): 591-4, 1981. [PUBMED Abstract]
  13. O'Brien B, Quigg C, Leong T: Severe cyanide toxicity from 'vitamin supplements'. Eur J Emerg Med 12 (5): 257-8, 2005. [PUBMED Abstract]
  14. Gostomski FE: The effects of amygdalin on the Krebs-2 carcinoma and adult and fetal DUB(ICR) mice. [Abstract] Diss Abstr Int B 39 (5): 2075-B, 1978.
  15. Schmidt ES, Newton GW, Sanders SM, et al.: Laetrile toxicity studies in dogs. JAMA 239 (10): 943-7, 1978. [PUBMED Abstract]
  16. Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979. [PUBMED Abstract]
  17. Calabrese EJ: Conjoint use of laetrile and megadoses of ascorbic acid in cancer treatment: possible side effects. Med Hypotheses 5 (9): 995-7, 1979. [PUBMED Abstract]
  18. Bromley J, Hughes BG, Leong DC, et al.: Life-threatening interaction between complementary medicines: cyanide toxicity following ingestion of amygdalin and vitamin C. Ann Pharmacother 39 (9): 1566-9, 2005. [PUBMED Abstract]
  • Updated: March 26, 2015