Medicines Can Interact with Other Drugs, Supplements & Foods/Drinks

If you take medication, you probably do so to improve your health. But, did you know that some prescription and over-the-counter (OTC) medicines can trigger a dangerous reaction if they're combined with certain other drugs, dietary supplements, and even everyday foods and beverages? To minimize the risk for drug interactions, the U.S. Food and Drug Administration (FDA) urges health care consumers to:

  • Learn as much as possible about the medicines they (or their loved ones) take,
  • Follow the directions on drug labels carefully, and
  • Ask their health care team (doctors, nurses, pharmacist) about other ways to reduce the risk for adverse reactions to medication.

Please note: the information below is not a complete list of possible reactions, so be sure to talk to your health care provider(s) about any medicines—prescription, over-the-counter, diet supplements, or herbal remedies—you take.

Drug/Drug Interactions

According to the FDA, about 40 percent of people in the United States have prescriptions for four or more medicines—and the more medications you take, the greater your risk for adverse drug interactions. Here is some important information from the FDA about common drug/drug interactions:

  • Amiodarone (Cordarone)/simvastatin (Zocor)—Amiodarone (used to treat heart rhythm problems) and simvastatin (a cholesterol-lowering medication) may cause a dangerous muscle condition called rhabdomyolysis, which can lead to kidney failure, when taken together and the dose of simvastatin is higher than 20 mg.
  • Amiodarone (Cordarone)/warfarin (Coumadin, Jantoven, generics)—Amiodarone can reduce the effects of the blood thinner warfarin and your health care provider may need to adjust your dosages.
  • Digoxin (Lanoxin)/ritonavir (Norvir)—The HIV/AIDS drug ritonavir may increase blood levels of the heart failure drug digoxin in patients who take both medications. High levels of can increase the risk for dangerous heart rhythm problems.
  • Antihistamines/other medications—Over-the-counter or prescription antihistamines—commonly used to treat allergic conditions—can interact with several other medications, including blood pressure medications, antidepressants, sedatives, and tranquilizers. Depending on which medicine you're taking, adverse reactions such as excessive sleepiness, impaired concentration, inability to focus, increased blood pressure, and rapid heart rate may occur.

Drug/Diet Supplement Interactions

According to the National Institutes of Health (NIH), about half of all adults in the United States use one or more dietary supplements regularly. Diet supplements include vitamins, minerals, amino acids, herbal products, and others.

Here are some common drug/supplement interactions from the FDA:

  • St. John’s Wort/medications—This common herb can affect blood levels of several common medications, including the heart drug digoxin (Lanoxin), the cholesterol drug lovastatin (Mevacor, Altocor), and sildenafil (Viagra; used to treat erectile dysfunction [ED, impotence]).
  • Ginseng/medications—This herb can interact with the blood thinner warfarin, and can increase the risk for bleeding in people who also take heparin, aspirin, and NSAIDs (nonsteroidal anti-inflammatory drugs like ibuprofen, naproxen, and ketoprofen). Ginseng also can cause headache, insomnia, nervousness, and hyperactivity in those who take monoamine oxidase (MAO) inhibitors (Nardil, Parnate) to treat depression and other conditions.
  • Ginkgo biloba/antiseizure medications—At high doses, Ginkgo biloba may decrease the effectiveness of anticonvulsants like carbamazepine (Tegretol, Equetro, Carbatrol) and valproic acid (Depakote), which are used to treat epilepsy/seizures.
  • Vitamin E/warfarin (Coumadin, Jantoven, generics)—Vitamin E supplements can increase the risk for bleeding in people who take warfarin.

Drug/Food & Drink Interactions

Foods and beverages can interact with medicines in many ways—affecting the way your body metabolizes and excretes some medications, and delaying, decreasing, or increasing medication absorption—so it's important to follow drug label recommendations and your health care provider's instructions carefully.

Here are some common drug/food and drink interactions from the FDA:

  • Alcohol/medications—Alcohol can interact with many prescription and over-the-counter medications. The FDA recommends avoiding alcohol if you are taking any type of medicine.
  • Chocolate/medications—Excessive amounts of chocolate can interact with MAO inhibitors. The caffeine in chocolate can also increase the effects of stimulants like methylphenidate (Ritalin) and decrease the effects of sedative-hypnotic drugs like zolpidem (Ambien).
  • Grapefruit & grapefruit juice/medications—According to the FDA, the number of drugs that interact with grapefruit products is not precisely known at this time. Talk to your health care provider if you take certain blood pressure medications, cyclosporine (to prevent organ transplant rejection), the anti-anxiety medicine buspirone (Buspar), the insomnia drug triazolam (Halcion), or anti-malaria drugs like quinine (Quinerva, Quinite) before eating/drinking grapefruit products.
  • Licorice/medications—Some forms of licorice can cause an adverse reaction in people who take digoxin (Lanoxin) to treat heart failure or heart rhythm disorders. Licorice also may reduce the effects of certain medications, including blood pressure drugs and diuretics (hydrochlorothiazide [Hydrodiuril], spironolactone [Aldactone]).

Tips to Avoid Drug Interactions

Read drug labels carefully, talk to your health care provider about all prescription and OTC medications—especially when you begin taking a new prescription drug—and follow his/her directions closely to reduce your risk for drug interactions. In addition, take the following steps as recommended by the FDA:

  • Keep all medications in their original containers.
  • Check with your health care provider or pharmacist before taking an OTC medication or dietary supplement—especially if you also take prescription medicine(s).
  • Fill all your prescriptions at the same pharmacy. If possible, use that pharmacy for your over-the-counter medicines and dietary supplements as well.
  • Make sure each member of your health care team—primary care doctor, specialist(s)—knows about all medicines you take.
  • Keep an accurate, up-to-date list of all medications—including the dosages, and how often you take them. Remember to include vitamin and mineral supplements and herbal remedies, as well as prescription and OTC drugs.

Source: U.S. Food and Drug Administration (FDA)

Publication Review By: the Editorial Staff at

Published: 08 May 2014

Last Modified: 28 Jan 2015