Both the pulp and juice of grapefruit contain components that inhibit liver enzymes from metabolizing some medications. By slowing the normal process of detoxification and elimination of certain prescription medications, grapefruit increases the potency of these drugs. Food-drug interactions should always be discussed with your health care provider when a new medication is added to your routine or your diet changes substantially.
Inhibits the Metabolism of Statins
Statins lower cholesterol by decreasing levels of low-density lipoproteins and triglycerides in the blood. At the same time, statins have the added benefit of increasing levels of high-density lipoproteins. A physician will prescribe a statin for patients with known heart disease or with risk factors for heart disease.
Avoid eating grapefruit or drinking grapefruit juice while taking a statin medication unless you have been instructed otherwise by your physician. Naringenin, a compound in grapefruit, interferes with the metabolism of statins by the liver enzyme cytochrome p450. This leads to excessive and dangerous concentrations of the drug in the bloodstream. Information posted on the website RxList warns this risk can increase with drinking more than one quart of grapefruit juice daily. Statin myopathy is a resulting complication of this adverse drug interaction. The symptoms are muscle pain and tenderness. In severe cases, muscle cells are damaged and release myoglobin into the bloodstream. Myoglobin is a protein that causes kidney damage.
Inhibits the Metabolism of Calcium Channel Blockers
Calcium channel blockers consist of a group of prescription medications that dilate arteries, reducing the pressure in the arteries. Physicians prescribe these drugs to treat high blood pressure, angina and cardiac arrhythmias such as atrial fibrillation.
Consult your physician before eating grapefruit or drinking grapefruit juice while taking a calcium channel blocker. Certain drugs within this group adversely interact with grapefruit. Drug interaction information provided by RxList alerts users that grapefruit doubles the plasma concentrations of calcium channel blockers. The compounds in grapefruit appear to inhibit the liver enzyme CYP 3A4 in the initial metabolism process. A serious consequence of higher levels of these drugs in your bloodstream is an increase in the expected effect of the drug. For example, concentrations of calcium channel blockers that are beyond therapeutic levels can drop blood pressure dangerously low.
Inhibits the Metabolism of Immunosuppressant Medications
Immunosuppressant medications prevent the body's rejection of a transplanted organ. Additional conditions treated with this group of drugs include rheumatoid arthritis, psoriasis and Crohn's disease. Immunosuppressants achieve their therapeutic effects by inhibiting T-cell activation, disrupting the synthesis of DNA and RNA and suppressing inflammation.
Avoid eating grapefruit or drinking grapefruit juice if you are taking this type of medication. Grapefruit and grapefruit juice adversely affect the metabolism of these drugs, increasing the plasma concentrations of the drug to potentially toxic levels.
Inhibits the Metabolism of Benzodiazepine, Sertraline and Carbamazepine
A group of depressant medications called benzodiazepines treat anxiety, insomnia and seizure disorders. Anesthesiologists use benzodiazepines for presurgical sedation. Sertraline is a selective serotonin reuptake inhibitor prescribed to treat major depressive disorders. Carbamazepine is an anticonvulsant medication used to treat epilepsy. Its additional analgesic property is specific for pain associated with trigeminal neuralgia.
The Harvard Medical School Family Health Guide warns that a single glass of grapefruit juice can inhibit the metabolism of these medications. Furanocoumin is component in grapefruit that binds to the enzyme CVP 3A4. During drug metabolism in the intestinal tract, furanocoumin can reduce CVP 3A4 by 47 percent. One third of the effect of a glass of grapefruit juice on certain prescription medications is still evident 24 hours after consumption.
