Amygdalin (laetrile), given to Fischer 344 rats in doses of 250, 500, and 750 mg/kg intraperitoneally daily for five days, caused mortalities of 30.8%, 44.1%, and 56.8%, respectively. The mode of death and the elevated serum cyanide levels in the dying animals strongly suggested cyanide poisoning as the cause of death. These findings seriously question the use of amygdalin in clinical medicine under any circumstances.
(JAMA 242:169-171, 1979)
Khandekar JD, Edelman H. Studies of Amygdalin (Laetrile) Toxicity in Rodents. JAMA. 1979;242(2):169-171. doi:10.1001/jama.1979.03300020039023