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Identifying Drug-Food Interactions

Edited by Adam Da Costa Gomes

Prescription and non-prescription medications can interact with each other and with foods, which can change the way they work in your body. Most drug interactions are not serious, but in some cases, these interactions can exacerbate or blunt the therapeutic intent of the drug, and commonly cause unintended side effects.

How Drug Interactions Occur

Drug interactions typically occur in two ways. First, interactions can occur pharmacodynamically when two agents act in a similar manner or affect the same receptor site. This can lead to a greater effect (if additive or synergistic) or a decreased effect (if antagonistic). Second, interactions can occur pharmacokinetically if one agent affects another drug’s absorption, distribution, metabolism, or excretion. Blood levels of a medication may be altered if taken with medications that affect metabolism. If drug metabolism increases, there is less medication in the body, which decreases the drug’s effectiveness. Vice versa, if drug metabolism decreases, there is more medication in the body, which increases the risk of side effects or toxicity.

It is crucial to be aware of all types of drug interactions because of their potentially lethal effects. Interactions can affect how the medication works by changing the amount of drug in your body, which can increase the risk of adverse drug effects and toxicity, or worsen existing medication conditions.

Knowing that interactions can occur pharmacodynamically or pharmacokinetically, it is now important to highlight which agents can interact with one another. There are three main types of drug interactions:

  • Drug-drug interactions are the most common type of drug interaction. The more medications in your therapy regimen, the higher the risk of an interaction between any two agents.

  • Drug-food/beverage interactions occur when a certain food or drink affects drug activity.

  • Drug-condition interactions happen when preexisting conditions affect the way a drug works in the body

Though all potential interactions are important to consider when taking any medications, we will focus on drug-food interactions in this article.

Common Drug-Food Interactions

Knowing what and how certain foods and beverages affect the way medications act in the body can help avoid unintended consequences. Listed below are some common drug-food interactions.

Statins and Grapefruit Juice

Many medications are metabolized by enzymes in the liver, which produce active and inactive metabolites depending on the medication. Statins are a class of medication used to lower cholesterol. If taken with grapefruit juice, furanocoumarin (a chemical found in grapefruits) can block enzymes in the liver that metabolize statins. Since these liver enzymes are no longer available to metabolize statins, this leads to a build-up of statins in the body and increases the risk of muscle pain and damage. Of note, this interaction only applies to atorvastatin (Lipitor), simvastatin (Zocor), and lovastatin (Mevacor). Rosuvastatin (Crestor), pravastatin (Pravachol), and fluvastatin (Lescol) are not metabolized by the aforementioned liver enzyme and can be a good alternative for those who regularly consume grapefruit juice.