Health Canada is advising the public not to take certain drugs with grapefruit juice. Although interactions between grapefruit juice and certain drugs are well documented in the medical and scientific literature, this information may be unknown to the public. There are several substances in grapefruit which interfere with the way the human body handles certain drugs. Consuming grapefruit juice (fresh or frozen) or grapefruit sections can increase, or less commonly decrease, the effects of some drugs, which could lead to serious or even life-threatening adverse reactions. As little as one glass of grapefruit juice (8oz/250mL) can cause this effect.