The presence of food in the stomach and small intestine can make certain drugs less effective or increase the risk of adverse effects, including prescription drugs and over-the-counter drugs. Along with food, herbal supplements, and certain medical conditions can also affect prescription and over-the-counter medications. Please keep reading to learn more about food-drug interactions. We will also list examples of common medications that should be taken on an empty stomach.

Should all medications be taken with food?

No, some medications need to be taken with food, while other drugs need to be taken without food. Some medications even need to be taken first thing in the morning before any meal. Your healthcare provider will give instructions about the medication dose, frequency, and whether to take it with or without food. Read the prescription label carefully and take your medication exactly as directed. Also, make sure to read the package label of over-the-counter medicines. If there are no instructions on the prescription label, it is a good idea to ask the pharmacist whether you need to take the medication with or without food. If prescribed a new medicine, you should remember to ask what food, beverages, and dietary supplements to watch out for to avoid harmful interactions.

Why are some medications not taken with food?

Certain foods can reduce the effect of a medicine. For example, food can affect the absorption of certain medications and lead to reduced bioavailability, making a particular drug less effective.

On the other hand, a potential interaction between food and certain medicines can increase the effect of the medicine and raise its blood level to dangerously high levels. When this happens, it does not mean the medicine works better; it is quite the opposite. A very high blood level of a medication can increase the risk of side effects which can sometimes be life-threatening.

If you are starting a new medication, ask your doctor whether to take it with or without food. If your doctor tells you to take a medicine without food or on an empty stomach, you should take it first thing in the morning, or at least one hour before meals or two hours after meals.

What medications should be taken on an empty stomach?

Food and beverages can affect how the body metabolizes many medicines. Here are some examples of medicines that doctors and pharmacists advise should be taken on an empty stomach.

Pain relievers

Tylenol (acetaminophen) is used to relieve mild to moderate pain and fever. Food can slow the absorption of acetaminophen, especially high-pectin-containing fruits like apples, pears, plums, guavas, oranges, and other citrus fruits. To get rapid relief from your symptoms, you should take Tylenol (acetaminophen) on an empty stomach. Also, avoid alcohol intake while on acetaminophen because it can increase the risk of liver damage.

This is not the case for all pain relievers. For instance, NSAIDs (nonsteroidal anti-inflammatory drugs) such as Advil (ibuprofen) and Aleve (naproxen), should be taken with food or milk to avoid stomach irritation.

Opiate medicine is another type of pain medicine used to treat severe pain. Oxycodone, hydrocodone, and morphine are a few examples of opiate pain relievers. Generally, you can take these pain medicines with or without food. However, food may help ease nausea if you have never taken this type of pain medicine before.

Certain antibiotics

A food-drug interaction can occur with certain antibiotics. Specifically, calcium-containing foods like dairy products, calcium supplements, and calcium-fortified foods can interact with tetracyclines (doxycycline, minocycline) and quinolones (ciprofloxacin). This can lead to reduced absorption of the antibiotic and failure to treat your infection properly.

Antihistamines

Antihistamines like loratadine (Claritin), fexofenadine (Allegra), cetirizine (Zyrtec), and cimetidine (Tagamet) are more effective when you take them on an empty stomach because of better absorption.

Newer antihistamines such as fexofenadine (Allegra) can also interact with orange, grapefruit, and apple juice. These acidic juices reduce the effectiveness of these medicines. Drinking fruit juice within one to two hours of taking these antihistamines can sometimes wipe out all their effects. Similarly, acidic juices can decrease the drug level of certain blood pressure medications. You should be cautious if you take a calcium channel blocker like amlodipine, diltiazem, or nifedipine. Other blood pressure medicines that should be steered clear from apple or orange juice are atenolol (Tenormin), a beta blocker, and aliskiren (Tekturna), a renin inhibitor. These drugs are used for the treatment of high blood pressure. You should drink fruit juice at least 2-4 hours away from these medicines to avoid food interactions that can render the drug ineffective.

Bronchodilators

The prescription drug theophylline is used to treat asthma and other respiratory conditions. This medicine can interact with many foods and drinks. For example, a high-fat meal can increase the level of theophylline in the body, and a high-carbohydrate meal can decrease it. Drinking alcohol while on theophylline can increase the risk of side effects such as headache, nausea, vomiting, and irritability. Caffeine-containing foods and beverages (tea, coffee, colas, chocolate) in large amounts while on theophylline can increase the risk of drug toxicity. Your doctor may ask you to avoid grapefruit juice while taking theophylline because it can increase the bioavailability of this drug, meaning a much larger amount of the drug is absorbed into the bloodstream, leading to adverse effects.

Blood thinners

The anticoagulant (blood thinner) medicine warfarin (Coumadin, Jantoven) has many food-drug interactions. For example, vitamin K-rich foods (broccoli, kale, and other green leafy vegetables) can make warfarin less effective. Warfarin works to thin the blood in people with health conditions that put them at higher risks of blood clots which can lead to stroke and heart attack. Vitamin K-containing foods counteract the action of warfarin. However, it may not be necessary for you to avoid kale and other leafy greens altogether. When your doctor or pharmacist creates a dosing regimen of warfarin for you, that warfarin dosing is based on your current intake of vitamin K-containing foods. Therefore, it is important to consume about the same amount of foods that are high in Vitamin K such as green leafy vegetables. Ask your doctor and pharmacist about foods and beverages you should watch out for to avoid potential interaction with warfarin, especially if you are new to warfarin.

Monoamine oxidase inhibitors

Monoamine oxidase (MAO) inhibitors are an older class of antidepressants and anti-Parkinson’s drugs that can have dangerous food-drug interactions. In particular, you should avoid eating an amino acid called tyramine. Eating tyramine-rich foods (aged cheeses, cured meats, red wine, ripe bananas, soy products, and fermented foods) while on monoamine oxidase inhibitors can lead to dangerously high blood pressure (hypertensive crisis).

Statins (cholesterol-lowering drugs)

If your doctor has started you on cholesterol-lowering medications called statins, they may give you certain dietary restrictions which you should follow carefully. Eating grapefruit or drinking grapefruit juice affects the liver’s ability to metabolize statins. This can lead to high levels of the drug in the body and an increased risk of side effects like muscle pain and liver damage. Examples of statins that should not be combined with grapefruit juice include atorvastatin (Lipitor), simvastatin (Zocor), and lovastatin (Mevacor).

Other examples of medications that have food-drug interactions with grapefruit include:

Antihistamines like fexofenadine (Allegra).
Calcium channel blockers for high blood pressure, such as nifedipine (Adalat CC, Procardia).
Anti-anxiety drugs like buspirone (BuSpar).
Steroid medicines like budesonide (Uceris and Entocort EC).
Other medications like amiodarone (Pacerone, Cordarone) prescribed for heart rhythm problems.
Drugs that prevent organ transplant rejection, such as cyclosporine (Neoral, Sandimmune) and tacrolimus (Prograf).

ACE inhibitors

ACE inhibitors are medicines used to treat high blood pressure. Taking these medicines with bananas and other potassium-rich foods like tomatoes and avocados can lead to high potassium levels. This is especially dangerous for people with kidney problems. Healthy kidneys remove toxins and extra fluids from the body while maintaining a good balance of minerals such as potassium, sodium, and phosphorus. When the kidneys are not working the way they’re supposed to, toxins and minerals are built up in the body leading to a high level of these minerals including potassium. Therefore, if you already have kidney diseases, eating high-potassium food will cause hyperkalemia (high blood level of potassium) causing fatigue, muscle pain, or even a heart attack. Examples of ACE inhibitors include lisinopril, ramipril, captopril, and moexipril.

Anti-tubercular drugs

Medications used for the treatment of tuberculosis, such as isoniazid, can have a food-drug interaction with tyramine, leading to decreased bioavailability of isoniazid. On the other hand, oleanolic acid, present in many foods and medicinal herbs, can increase the blood levels of isoniazid and other anti-tuberculosis drugs. High-fat meals can lead to lower blood levels of cycloserine, another anti-tubercular drug, leading to inadequate tuberculosis treatment.

Thyroid disease medications and heart medications

Levothyroxine is a prescription drug used to treat hypothyroidism, a condition where your thyroid gland does not make enough thyroid hormones. Eating high-fiber foods like walnuts, cottonseed meal, soybean flour, dietary fiber, calcium, and calcium-fortified foods and beverages can decrease the absorption of levothyroxine. Interestingly, grapefruit juice does not have a significant effect on levothyroxine. Besides the high-fiber food, you should separate levothyroxine from caffeinated beverages. Therefore, it is best to take levothyroxine first thing in the morning, 30 minutes before breakfast, or any caffeinated beverages like coffee or tea.

Besides levothyroxine, high-fiber foods also have food-drug interactions with a heart medication called digoxin. You should take digoxin 2 hours before or after eating high-fiber foods.

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