Author: Charles Frank

What is a Drug Interaction? NIH

what is drug interaction

Always check to see if your medicines interact with alcohol before you combine the two. But most drug labels and patient handouts don’t list every possible drug interaction. They can also answer any questions about medical terms or jargon on the drug packages. Because there’s not always formal studies, some drug interactions with herbal products may not be known. Also, remember that herbal supplements are not subject to FDA review and have not usually been tested in clinical studies to prove their effectiveness or safety.

If you have questions about food or drink interactions with your medicines, your pharmacist is a great resource. More and more medicines have interactions with food and drinks. In many cases it will cause the levels of drugs to increase in the blood, which can cause side effects. Pharmacists are experts on medicine safety, and they can work with your doctors to help you avoid drug interactions. For example, if you have two doctors and they separately prescribe drugs that interact, your pharmacist can warn them — and you — before you have a problem.

For example, if two drugs can each make you sleepy, taking them together can make you more or dangerously sleepy. Enter search terms to find related medical topics, multimedia and more.

U.S. Food and Drug Administration

Food can affect the absorption of some HIV medicines and increase or reduce the concentration of the medicine in the blood. Depending on the HIV medicine, the change in concentration may be helpful or harmful. Directions on how to take HIV medicines specify whether to take the medicine with food or on an empty stomach. Some HIV medicines can be taken with or without food, because food does not affect their absorption. For example, St. John’s Wort, CoenzymeQ10, and even melatonin can interact with medicines like antidepressants, blood thinners like warfarin or even alcohol. These interactions can be just as serious as prescription medicines.

  1. The effects, desired and undesired, of all drugs taken should be determined because these effects usually include the spectrum of drug interactions.
  2. Also, remember that herbal supplements are not subject to FDA review and have not usually been tested in clinical studies to prove their effectiveness or safety.
  3. In pharmacokinetic interactions, a drug usually alters absorption, distribution, protein binding, metabolism, or excretion of another drug.
  4. Some vitamins and dietary supplements interact with medicines, too.
  5. Always consult your healthcare provider about how drug interactions should be managed before making any changes to your current prescription.

Many of these products, just like prescription drugs, may have serious drug interactions. Over-the-counter drug labels include information about possible drug interactions and the medication’s active ingredients. Prescription medications usually come with a sheet that explains what the drug is and how to take it safely. Not all drugs interact, and not every interaction means you must stop taking one of your medications. Always consult your healthcare provider about how drug interactions should be managed before making any changes to your current prescription.

It could make your medication stop working, become less effective, or too strong. Conditions, such as kidney disease, hepatitis, and pregnancy, can affect how the body processes HIV medicines. The dosing of some HIV medicines may need to be adjusted in people with certain medical conditions. A drug interaction can affect how a drug works or cause unwanted side effects.

Drugs & Medications Resources

There are several ways that drugs can interact with one another. Review the Medication Guide, prescription information, warning labels, and Drug Facts Label with each new prescription or over-the-counter product you use. Over-the-counter medicines also contain a Drug Facts label that helps to explain the medicine. If you do not understand your directions, ask a healthcare professional for help. Compounds that increase the efficiency of the enzymes, on the other hand, may have the opposite effect and increase the rate of metabolism. When two drugs can cause the same side effect and are used at the same time, they might cause more of that side effect.

what is drug interaction

You could show them a list of the meds you’re taking, or bring the medication packages to your appointment. Most drugs that you swallow enter your blood through your intestines. Sometimes a drug or supplement can block or trap another drug in the intestine before it can be absorbed. For example, supplements like calcium and iron can prevent absorption of thyroid meds. When a medication works right, it boosts your health or helps you feel better.

But a drug can bring on problems if it doesn’t mix well with something else you put into your body, like another medication, a certain food, or alcohol. Information may change as new information is learned about medications, so it’s important to review the information frequently. Ask your pharmacist if you need a copy of any of this information.

What Are the 3 Types of Drug Interactions?

Alcohol is itself a drug and may cause central nervous system side effects, like drowsiness, dizziness or fainting. When you combine it with other drugs that have similar side effects, your breathing may slow to dangerous or deadly levels. You might become unsteady and at risk for a fall or broken bone. Extra drowsiness can make it very dangerous for you to drive or perform hazardous activities. In therapeutic duplication, 2 drugs with similar properties are taken at the same time and have additive effects. For example, taking a benzodiazepine for anxiety and another benzodiazepine at bedtime for insomnia may have a cumulative effect, leading to toxicity.

When your doctor prescribes a new drug, discuss all OTC and prescription drugs, dietary supplements, vitamins, botanicals, minerals and herbals you take, as well as the foods you eat. Ask your pharmacist for the package insert for each prescription drug you take. The package insert provides more information about potential drug interactions. Be sure to check your prescription drugs, as well as your over-the-counter (OTC) medicines, herbals, and dietary supplements like vitamins and minerals for alcohol interactions. Some cough and cold medicines may also contain alcohol, so be sure to check the labels.

In pharmaceutical sciences, drug interactions occur when a drug’s mechanism of action is affected by the concomitant administration of substances such as foods, beverages, or other drugs. A popular example of drug-food interaction is the effect of grapefruit in the metabolism of drugs. For instance, it can be dangerous to drink alcohol while you’re on certain medications. Some vitamins and dietary supplements interact with medicines, too.


The easiest way to lookup drug information, identify pills, check interactions and set up your own personal medication records. If you find you are at risk for an interaction, call your doctor or pharmacist. They will know if the interaction is serious and can recommend the next best step. Some symptoms may be minor, while others can be serious or life-threatening. The function of the enzymes can either be stimulated (enzyme induction) or inhibited (enzyme inhibition).

It also has a way to get rid of drugs, usually though your urine. Other drugs may speed up, slow down, or even completely block these functions. When this happens, the amount of drug in your body may increase (similar to taking too much) or decrease (similar to taking too little). Active ingredients are the chemicals in medications that treat your condition or symptoms. For example, taking a cough medicine (antitussive) and a drug to help you sleep (sedative) could cause the two medications to affect each other.

The symptoms of a drug interaction can vary a lot, depending on the drugs you’re taking and how they’re interacting. Sometimes you might not even know right away that an interaction is happening. It’s important to take your medication as directed by your doctor or pharmacist. If two meds interact, spacing them apart during the day may not stop them from interacting and could lead to new or worse problems. To avoid an interaction, your doctor may need to change your dose or prescribe a different medication.

These may be competitive antagonists, if they compete with the main drug to bind with the receptor. Or uncompetitive antagonists, when the antagonist binds to the receptor irreversibly. The drugs can be considered Heterodynamic competitors, if they act on distinct receptor with similar downstream pathways. Pharmacodynamic interactions are the drug-drug interactions that occur at a biochemical level and depend mainly on the biological processes of organisms. These interactions occur due to action on the same targets, for example the same receptor or signaling pathway. The following are examples of drug interaction warnings that you may see on certain OTC drug products.