How Does Grapefruit Affect Certain Medicines?

On many prescription medication labels you will see a warning against consuming grapefruit while taking that medication. The potential interaction of grapefruit and medications has been a hot topic for many years now, and the list of medicines that are affected by grapefruit  consumption has grown.

What many pharmacies or medical personnel don’t tell you is how and why grapefruit can be dangerous when mixed with certain medicines. What do you need to know?

Grapefruit and Your Digestive System

There are special enzymes present in your small intestinal wall that enable medicines to be absorbed into the body, but grapefruit can block these enzymes or even destroy the medication. This results in smaller amounts of the medicine entering the body, but higher levels occurring in the bloodstream. This process can enhance side effects of these medicines, but also of course make them less effective.

What Drugs Are Affected By Grapefruit Consumption?

The following list of drugs features the medications most commonly affected by the consumption of grapefruit. If you are unsure whether a medication you take interacts negatively with grapefruit, or for some reason you cannot avoid taking grapefruit, discuss with your doctor the potential impact of eating or drinking grapefruit and any medicines you may be taking.

• Cholesterol Drugs (statins) – atorvastatin, lovastatin, Lipitor, Zocor, simvastatin, Vytorin.
• Calcium Channel Blockers (prescribed for high blood pressure) – felodipine, nimodipine, nicardipine, nisoldipine, verapamil.
• Antihistamines – fexofenadine.
• Intestinal medicines – cisapride.
• Psychiatric drugs – triazolam, buspirone, Tegretol, diazepam, midazolam, sertraline.
• Pain drugs – methadone (also prescribed to recovering drug addicts).
• Antiarrhythmics prescribed for a better heart rhythm – disopyramide, amiodarone.
• Immune suppressants – tacrolimus, Cyclosporine
• Impotence or erectile dysfunction drugs – Viagra.
• HIV drugs - saquinavirsa.

Other drugs that can be affected by the consumption of grapefruit include:

• Amlodipine
• Ergotamine
• Amitriptyline
• Quinidine
• Tadalafil (Cialis)
• Tylenol
• Codeine
• Lamotrigine
• Losartan
• Omeprazole
• Ocycodone
• Quetiapine
• Tamoxifen
• Trazodone
• Verapamil
• Warfarin
• Zolpidem
• Levothyroxine
• Imatinib
• Fluvoxamine
• Fexofenadine
• Exemestane
• Aromasin
• Tarceva
• Duloxetine
• Praziquantel
• Apremilast
• Vardenafil
• Nimodipine
• Quinidine
• Dronedarone
• Propafenone
• Carvedilol
• Benzodiazepines
• Amphetamines
• Ritonavir
• Sertraline
• Caffeine
• Dextroamphetamine
• Levoamphetamine
• Methamphetamine
• Methylphenidate

READ Health Benefits of Citrus Fruits: Oranges, Grapefruits, Lemons and Limes

There are potentially more drugs affected by a negative interction with grapefruit than are mentioned here, so if you are on any medication, it is essential you check with your health professional if it is okay to eat or drink grapefruit or not.

Timing of Medication and Grapefruit: Is Consuming Grapefruit OK if You Just Wait a While?

Many people think that if they just don’t take the medicine at the same time as the grapefruit, any negative interaction the medication's package insert warns about won’t occur, but this is not the case. Delaying your grapefruit consumption until well after you took your meds may lower the severity of the interaction, but not always.

The enzymes in the wall of the small intestine can stay blocked for more than 24 hours after eating grapefruit flesh or juice, so it is also possible that that slice of grapefruit or glass of juice will still actively harm you. This caution also applies to any medications that are only taken once a day. These are usually slow release drugs, and will still be affected by the consumption of grapefruit.