Drug and Food Interactions

Last Updated: July 1, 2003

Many medicines have powerful ingredients that interact with the human body in different ways and your diet can sometimes have a significant impact on a drug’s ability to work in the body. Certain foods, beverages, alcohol and caffeine can interact with medicines.

Be sure to follow the directions given to you by your doctor or pharmacist and ask any questions you may have about interactions with foods or other drugs.

Here are some drugs and examples of how they can interact with alcohol and food.

ANTICOAGULANTS
Food: Vitamin K produces blood-clotting substances and may reduce the effectiveness of anticoagulants. So limit the amount of foods high in vitamin K (such as broccoli, spinach, kale, turnip greens, cauliflower and brussel sprouts).

High doses of vitamin E (400 IU or more) may prolong clotting time and increase the risk of bleeding. Talk to your doctor before taking vitamin E supplements.

ANGIOTENSIN CONVERTING ENZYME (ACE) INHIBITORS
Food: Food can decrease the absorption of captopril and moexipril. So take captopril and moexipril one hour before or two hours after meals. ACE inhibitors may increase the amount of potassium in your body. Too much potassium can be harmful. Make sure to tell your doctor if you are taking potassium supplements or diuretics (water pills) that may increase the amount of potassium in your body. Avoid eating large amounts of foods high in potassium such as bananas, green-leafy vegetables and oranges.

ANTIHISTAMINES
Alcohol: Some antihistamines may increase drowsiness and slow mental and motor performance. Use caution when operating machinery or driving.

BETA BLOCKERS
Alcohol: Avoid drinking alcohol with propranolol / INDERAL because the combination lowers blood pressure too much.

BRONCHODILATORS
Food: The effect of food on theophylline medications can vary widely. High-fat meals may increase the amount of theophylline in the body, while high-carbohydrate meals may decrease it. It is important to check with your pharmacist about which form you are taking because food can have different effects depending on the dose form (e.g., regular release, sustained release or sprinkles.) For example, food has little effect on Theo-Dur and Slo-Bid, but food increases the absorption of Theo-24 and Uniphyl which can result in side effects of nausea, vomiting, headache and irritability. Food can also decrease absorption of products like Theo-Dur Sprinkles for children.

Caffeine: Avoid eating or drinking large amounts of foods and beverages that contain caffeine (e.g., chocolate, colas, coffee, tea) because both oral bronchodilators and caffeine stimulate the central nervous system.

Alcohol: Avoid alcohol if you’re taking theophylline medications because it can increase the risk of side effects such as nausea, vomiting, headache and irritability.

DIURETICS
Food: Diuretics vary in their interactions with food and specific nutrients. Some diuretics cause loss of potassium, calcium, and magnesium. Triamterene, on the other hand, is known as a “potassium-sparing” diuretic. It blocks the kidneys’ excretion of potassium, which can cause hyperkalemia (increased potassium). Excess potassium may result in irregular heartbeat and heart palpitations. When taking triamterene, avoid eating large amounts of potassium-rich foods such as bananas, oranges and green leafy vegetables, or salt substitutes that contain potassium.

NARCOTIC ANALGESICS
Alcohol: Avoid alcohol because it increases the sedative effects of the medications. Use caution when motor skills are required, including operating machinery and driving.

NITRATES
Alcohol: Avoid alcohol because it may add to the blood vessel-relaxing effect of nitrates and result in dangerously low blood pressure.

Source: U.S. Food and Drug Administration • Center for Drug Evaluation and Research

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