Grapefruit and grapefruit juice are metabolized by the same enzymes in the liver that break down many drug compounds. Eating grapefruit leaves less enzymes available to break down the medication, and the amount of drug remaining in the blood remains high. With more drug remaining in the body and for a longer period of time, there is the potential for dangerous side effects to occur.
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Blood Pressure Medications
According to physicians at the Harvard Medical School, grapefruit and grapefruit juice interact with a number of calcium channel blocker medications. These are typically prescribed to treat high blood pressure and angina. Common calcium channel blockers that interact with grapefruit include felodipine and nifedipine. The related drugs verapamil, diltiazem and amlodipine are not affected by grapefruit.
According to Harvard Medical School doctors, the effects of just one glass of grapefruit juice on the availability of liver enzymes persist for many hours. Some individuals will need to stop drinking grapefruit juice completely in order to avoid a dangerous drug interaction. Check with a health care provider to determine whether you should stop consuming grapefruit, reduce your consumption or change the timing of your medication to avoid consuming both simultaneously. Orange juice is a good alternative for those who enjoy citrus juice.
Grapefruit interacts with a variety of other types of medication. Of the statin medications that are commonly used to treat high cholesterol, atorvastatin, simvastatin and lovastatin levels are increased by grapefruit. Benzodiazepines, a class of medications used to treat anxiety and insomnia, interact with grapefruit. Certain neurological and psychiatric medications are also processed by the same liver enzymes as grapefruit. Check the instructions provided by your pharmacist or consult your doctor to learn more about the specific cautions that apply to your medication.