Canada. Health Canada is advising the public not to take grapefruit or its juice (fresh or frozen) with certain drugs since several substances in grapefruit may interfere with their metabolism, leading to higher blood levels of these drugs with serious and even life-threatening adverse reactions. Affected products include (but not limited to) drugs used in treating medical conditions such as angina, anxiety, cancer, convulsions, depression, erectile dysfunction, gastrointestinal reflux, high blood pressure, high lipid cholesterol levels, HIV/AIDS, infections, irregular heart rhythms, organ graft rejections and psychotic problems. As little as one glass of grapefruit juice can cause an increased blood drug level and the effects can last for three days or more. Health Canada has issued several communication documents to remind health professionals of possible interactions between grapefruit and drugs. In addition, Health Canada is working with drug manufacturers whose products are adversely affected by grapefruit, to ensure that the relevant information is placed on the product label.

Reference:

Health Canada Warnings/ Advisories, 21 Jun 2002.
Available from URL: http://www.hc-sc.gc.ca