How Grapefruit Juice Affects Prescription Drugs: What You Need To Know

Grapefruit is a nutritious fruit, packed with vitamin C and potassium, essential nutrients for good health. However, it can interact with certain prescription and over-the-counter medications, affecting how these drugs work in the body. These interactions may lead to serious side effects, prompting the U.S. Food and Drug Administration (FDA) to require warning labels on some medications about consuming grapefruit or grapefruit juice.

Here are a few examples of medications that grapefruit juice can interact with:

• Statins like Zocor (simvastatin) and Lipitor (atorvastatin) that lower cholesterol
• Blood pressure medications, such as Procardia and Adalat CC (nifedipine)
• Organ transplant rejection drugs, including Neoral and Sandimmune (cyclosporine)
• Anti-anxiety medications like BuSpar (buspirone)
• Corticosteroids for Crohn’s disease or ulcerative colitis, such as Entocort EC and Uceris (budesonide)
• Heart rhythm drugs like Pacerone and Cordarone (amiodarone)
• Antihistamines, such as Allegra (fexofenadine)

Not all drugs in these categories are affected by grapefruit juice, and the severity of the interaction varies based on factors like the person, the drug, and the amount of juice consumed. To avoid issues, consult your doctor or pharmacist and review any drug information provided with your medication.

How Grapefruit Juice Affects Medications

According to Dr. Shiew Mei Huang from the FDA, grapefruit juice can increase the amount of a drug in the bloodstream, leading to potential side effects. For example, drinking excessive grapefruit juice while on certain statins can cause high drug levels, which could damage the liver and muscles, potentially leading to kidney failure.

Certain drugs are metabolized in the body with the help of an enzyme called CYP3A4. Grapefruit juice can block this enzyme’s activity, causing more of the drug to stay in the bloodstream longer, increasing the risk of side effects.

However, not everyone is affected the same way. The level of CYP3A4 in the intestine varies from person to person, so the impact of grapefruit juice can differ, even for individuals taking the same drug.

Some Drugs Are Affected Differently by Grapefruit Juice

While grapefruit juice has been known for decades to cause high drug levels, recent studies show it can also reduce the effectiveness of some drugs. For instance, grapefruit juice can reduce the amount of fexofenadine (Allegra) in the bloodstream, making it less effective in treating allergy symptoms. The drug’s label advises against taking it with grapefruit, orange, or apple juice.

The reason for this opposite effect is that grapefruit juice can interfere with proteins known as drug transporters, which help move drugs into cells for absorption. By blocking these transporters, less of the drug enters the bloodstream, which can reduce its effectiveness.

Understanding Drug Interactions

Grapefruit juice can either increase or decrease the amount of certain drugs in the body, depending on how the drug is processed. In some cases, it blocks enzymes that break down the drug, causing higher drug levels and more side effects. In other cases, it affects transporters, reducing the drug’s absorption and effectiveness.

How to Stay Safe

To protect yourself from potential interactions, ask your doctor or pharmacist whether grapefruit juice affects your medication. Always read the medication guide or patient information sheet that comes with your prescription to find out if grapefruit juice is a concern. The Drug Facts label on over-the-counter medications will also indicate if grapefruit or other fruit juices should be avoided.

If you’re advised to avoid grapefruit juice, be cautious about drinks flavored with fruit juices or other fruits like Seville oranges, pomelos, and tangelos, which may have similar effects.

Stay informed and discuss any concerns with your healthcare provider to ensure your medications work safely and effectively.