Grapefruit: Can it Interact with Medications?
 (www.mayoclinic.com , 10/31/02)

Grapefruit contains many health-promoting nutrients (like lycopene), but it also contains substances that interact with certain prescription medicines to increase the likelihood of side-effects. The increased risk occurs because chemicals in grapefruit may prevent a drug from breaking down in the gut and/or liver, thereby creating blood levels of that medication that are higher than what the prescribing doctor intended. Drugs known to interact with grapefruit to cause serious side-effects include: antiseizure drugs, antidepressants, bensodiazepines, calcium channel blockers, HIV pretease inhibitors, HMG-CoA reductase inhibitors, immunosuppressant drugs and anti-arrhythmic medication.