Frequently Asked Questions (FAQs)

Any time you take more than one medication, or even mix it with certain foods, drinks, or over-the-counter products (including vitamins and minerals), you run the risk of a drug-drug interaction.

Most drug interactions are not serious, but because there are some that can be serious, it is important to understand the potential outcome before taking your medications.

The more medicines you take, the more likely it is that your medicine will interact with another medicine. Drug interactions can reduce the effectiveness of your medication, increase minor or serious unexpected side effects, or even increase the blood level and possible toxicity of a particular drug.

Drug interactions can occur in several ways:

• A pharmacodynamic interaction occurs when two drugs given together act at the same or similar receptor site and result in a greater (additive or synergistic) effect or a reduced (antagonistic) effect.
  
• A pharmacokinetic interaction can occur when one drug affects the absorption, distribution, metabolism, or excretion of another drug. Examples can help explain these complicated mechanisms:
  
  • Absorption: Some drugs can alter the absorption of another drug into your bloodstream. For example, calcium can bind with some medications and block absorption. Similarly, many medications cannot be taken with milk or dairy products because they will bind to the calcium. Medications that affect gastrointestinal motility, pH, or natural flora may also cause drug interactions.
    
  • Distribution: Interactions due to protein binding can occur when two or more drugs that bind strongly to a protein compete for a limited number of binding sites on plasma proteins. The drug that is less bound to protein then acts more strongly.
    
  • Metabolism: Drugs are usually eliminated from the body as an unchanged (parent) drug or as a metabolite that has been altered in some way. Enzymes in the liver, usually the CYP450 enzymes, are often responsible for breaking down drugs that are eliminated from the body. Some drugs activate or inhibit the CYP450 system, which can lower or raise blood concentrations of drugs that are substrates of this system.
    
  • Excretion: Some drugs may decrease kidney function and therefore decrease the excretion of other drugs excreted by the kidneys. You may need a dose adjustment or more frequent monitoring by your doctor to use both medicines safely together.

Drug interactions are important to monitor because they:

• Can affect how your medication works by changing the amount of the drug in your blood;
• Could put you at risk for side effects and toxicity;
• May worsen a medical condition that you may already have.

Checking for a drug interaction before it occurs can dramatically reduce your chances of a problem. Usually, your doctor and pharmacist have already done this with your prescription medications, but it is a good idea to check and learn about these medications yourself.

If you take over-the-counter medications, including vitamins, herbs or dietary supplements, you should also check these products for interactions with your prescription medications. Ask your pharmacist or doctor for advice if you are confused by the medical jargon.

Drug interactions can also contribute to healthcare costs, as a serious drug interaction can lead to injury, hospitalization, or, in rare cases, fatalities.

Not all drug interactions are bad. Some drugs may be better absorbed when taken with food or may achieve more favorable blood levels when taken with other drugs that affect metabolic enzymes.

Major drug interactions that are life-threatening are infrequent but are a serious concern. Most drug interactions listed in package labeling may be theoretical and based on a drug’s pharmacology.

However, if you can avoid a possible drug interaction by choosing another drug, that is always the best choice.

Since most people do not know whether two or more medications may interact, it is important to check the status of drug interactions with each new medication. For some drugs, stopping the medication may even affect the exposure of other drugs in your bloodstream. Being proactive in your own health, checking for drug interactions and discussing concerns with your healthcare provider can be life-saving.

How often a drug interaction occurs and your risk of a drug interaction also depends on factors such as:

• Total number of medications you take;
• Age, kidney, and liver function;
• Diet and possible drug interactions;
• Medical conditions;
• Metabolic enzymes in your body and your genetics.

Remember that alcohol, caffeine and illegal drugs can also lead to serious drug interactions.

Taking a medication prescribed to someone else or purchased over the Internet can also be dangerous and can lead to unexpected drug interactions.

Communication with your healthcare provider is essential to help prevent drug interactions. Keep a current list of your medications, over-the-counter medications, vitamins, herbs and medical conditions.

Share this list with your doctor, pharmacist and nurse at each visit so they can also screen for drug interactions.

Review the medication manual, prescription information, warning labels and drug facts label with each new prescription or over-the-counter product. Labeling can change as new drug information is learned, so it is important to review the information regularly.

It is always best to ask your healthcare provider for the latest information on drug interactions.

However, you can also use our online drug interaction checker to learn more about possible drug interactions. This tool explains what the interaction is, how it occurs, the level of significance (major, moderate, or minor) and usually a suggested course of action. It also shows possible interactions between your chosen drug(s) and food, beverages, or a medical condition.