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

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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.

Grapefruit – To Have Or Not To Have

Can You Just Have a Little Grapefruit?

No. Incredibly, it does not take a lot of grapefruit to cause a harmful interaction with many medicines. It only takes about 200mls of juice to block the digestive enzymes in the small intestine, leading to toxic levels in the bloodstream of the medication. So, not even a sip or a nibble is safe with certain medicines.

What About Other Citrus Fruits?

Many other types of citrus fruit are absolutely safe to eat without causing the same interactions as grapefruit. The only other citrus fruits that you need to be cautious with are pomelo, limes and the Seville orange. Before consuming these fruits, check with your doctor to see if they are safe if you are on a medication that "bans" grapefruit.

Effects of Interactions between Grapefruit and Medications

What effects occur after you consume grapefruit will depend largely on the type of drug or medication you are taking. If you are taking a drug for your heart rate or rhythm, you may end up with an abnormal rate or rhythm because consuming grapefruit renders the medication ineffective, or rather too effective. Other reactions can include hemorrhage (bleeding) from the stomach, damage to the kidneys, breakdown of muscle, breathing difficulties, low blood pressure, dizziness, and sedation.

Grapefruit: To Take or Not To Take?

The risk associated with a medication and grapefruit interaction is a serious one, and it should not be treated lightly. Many of the medicines that are known to interact with grapefruit are prescribed for particularly serious medical conditions, and without the right dosages, the result could be deadly.

Often with medicines, too much can be just as dangerous as not enough, which is why levels of many medications are often regularly checked by your doctor to make sure the levels are therapeutic and not harmful.

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Grapefruit has long been touted as a healthy addition to your diet, and a lot of people have made claims that it assists with weight loss and keeps your body healthy by flushing toxins out through your urine. However, if you are taking medication regularly, this risk far outweighs the potential positives you may gain from the grapefruit.

It’s important to remember that it only takes a very small amount of grapefruit juice, less than a cup, to have a disastrous effect on your medication. It doesn’t matter whether there is a big break between taking the medicine and eating grapefruit, the effect can still be the same. It is also vital to know that other citrus fruits such as limes, Seville oranges and Pomelo can also cause the interaction, so they too should be avoided. The main thing to think about is, if in doubt, check it out with your doctor.