Most people know that grapefruit and grapefruit juice can interfere with medications, but did you know that you might have to wait as long as 24 to 48 hours before taking a drug after having the fruit? Grapefruit inhibits the important intestinal enzyme CYP3A4, which is needed to break down many medicines properly. Different people have differing amounts of the enzyme and so are affected to a greater or lesser degree. Medicines known to be affected by grapefruit include…
Calcium channel blockers, including nifedipine (Adalat or Procardia), verapamil (Calan, Covera-HS, Isoptin, Verelan) and others.
Cholesterol-lowering drugs, including atorvastatin (Lipitor), lovastatin (Mevacor) and simvastatin (Zocor)—but not pravastatin (Pravachol).
Sleeping pills and antianxiety drugs, such as buspirone (Buspar), diazepam (Valium) and others.
Heart medicines, such as amiodarone (Cordarone, Pacerone) and quinidine (Quinaglute, Quinidex).
Transplant drugs, such as cyclosporine (Neoral, Sandimmune) and tacrolimus (Prograf).
Estrogen, including birth-control pills.
Epilepsy drug carbamazepine (Tegretol).
Studies of grapefruit’s effects on medicines are continuing. Many other drugs may be affected to a greater or lesser degree.