Drug-Food Interactions

Christian Hartman, BSPharm, RPh, and Samantha Duong, PharmD, RPh
Published Online: Sunday, February 1, 2004

Medications are prescribed to treat and/or cure illnesses. They should be taken properly so that they give you the greatest benefit. Your physician or pharmacist will often discuss with you potential interactions of a drug with another drug. Your pharmacist will screen new medications against the ones you are already taking for potential drug interactions and precautions.

In addition to medications, foods may alter the effects of drugs by interfering with the manner in which the drugs are intended to work. The optimal effect of a drug may not be achieved, and thus you may receive an overdose or an underdose. Although some interactions are harmless, others can lead to serious side effects that have the potential to cause injury.

Furthermore, food interactions can prevent you from receiving the intended dosage of medication needed and can prolong your illness. It is important to realize that food?drug interactions can occur with prescription medications, nonprescription (over-the-counter) medications, vitamins, and herbal products.

How Do Drug?Food Interactions Occur?

For the most part, food interactions with drugs occur in 3 ways: (1) by reducing the rate or extent of absorption of the drug, (2) by increasing the rate or extent of absorption of the drug, or (3) by chemical interactions. Food can prevent a drug from being absorbed properly in the small intestine, thus limiting its effectiveness. In addition, direct interactions can result in serious side effects that may need immediate medical attention.

What Should You Do?

With any medication, it is important to read all the instructions before taking it, and to consult your physician or pharmacist if you have any questions. The written information your pharmacist provides will outline important details about taking your medication. In addition to the written information, your doctor or pharmacist should be able to clarify and provide more comprehensive information. (Also see Tables 1 and 2.)

In the event that you experience an adverse event, you should contact your doctor immediately. Often there are general signs and symptoms that may help you identify that something is going wrong. Some of these signs include shortness of breath, a flushed feeling, a faster or slower heart rate, an upset stomach, sleepiness, vision problems, constipation, and headaches.

Can Beverages Cause Problems?

It is also important to consider possible interactions with beverages. Some ingredients in beverages can interact with your medication and cause harm and/or prolong illness. You should look on the labels of beverages for a complete list of their ingredients.

As a general rule, it is best to take most medications with water. In addition, alcohol should always be avoided when taking any medication. Alcohol can decrease absorption of the medication, dissolve the coating of some tablets and capsules, interact directly with medications, and increase drowsiness. For example, alcohol can interact with metronidazole (an antibiotic) and cause flushing, a faster breathing rate, a faster pulse rate, and even death.

What Should You Remember Most?

The benefits of avoiding drug?food interactions include maximizing the efficacy of the drug in addition to reducing adverse effects and side effects. Depending on the drug, you may have to separate the times between taking a drug and eating, or take the drug and food at the same time, or even avoid a certain food altogether. It is important to read information about each medication you are taking and to contact your doctor immediately if you experience an unwanted side effect.



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