When Drugs Don’t Mix: Avoiding Drug Interactions

It may surprise you to learn that the average American gets at least 12 prescriptions annually – the number is even higher for those over 65 years old. And this average does not include over-the-counter medicines, dietary supplements, or herbal products. When two or more different medicines are taken at the same time, you’re at risk for having a drug-drug interaction that could make your medicines less effective, cause unexpected side effects, or even increase the action of a particular drug. Even beverages, such as alcohol, and foods such as grapefruits, can also affect how certain medicines work. If a drug interaction has an undesired effect, this is called an adverse drug interaction.

While it’s reassuring to know that most drug interactions don’t actually result in clinically important adverse effects, some may have severe consequences and even lead to death. So what are some common drug interactions, risk factors, and how can drug interactions be prevented and recognized if they do occur?

What are Some Common Drug Interactions?

These are not complete lists of interactions, so check with your doctor or pharmacist to see if your medication is affected.

  • Food-related drug interactions:
    • Grapefruit juice raises the level of certain medicines, such as some statins and antidepressants increases the risk of side effects by interfering with their metabolism.
    • Foods that contain tyramine, such as cheeses, especially strong, aged or processed cheese, can interact with certain medicines used for depression and for blood pressure control.
    • Medicines used to prevent and treat osteoporosis should be taken on an empty stomach with a full glass of plain water because the drugs are poorly absorbed.
    • Over-the-counter-related drug interactions:
      • Antacids, calcium, and iron lower the amount of tetracycline and certain other antibiotics that the body absorbs. Taking these products at least two hours apart can prevent this interaction.
      • Nasal decongestants can cause problems in persons with heart disease, high blood pressure, thyroid disease, or diabetes
      • Antihistamines may cause problems in persons with glaucoma or those experiencing difficulty in urination due to an enlarged prostate gland.
      • Prescription Drug-Drug Interactions:
        • Combining medicines that make you drowsy, such as sleeping pills, narcotic pain pills or many antihistamines with each other or with alcoholic beverages can cause excessive sleepiness and make driving a car or operating machinery dangerous.
        • Warfarin, a blood thinner or anticoagulant, as well as medicines for epilepsy are prone to drug interactions. These drugs can even interact with over-the-counter medicines that prevent or relieve heartburn associated with acid indigestion.  Careful monitoring and review of any changes in your medication regimen or diet with your health provider is important.
        • There are thousands of drugs and even more possible combinations. Luckily, there are useful guides available to check all your medicines for potential drug interactions, such as the Drug interaction checker


What are Risk Factors for Drug Interactions?

  • Multiple drugs, prescribers, pharmacies. The more medicines someone takes, the higher the risk of drug interactions. Also, if you use multiple doctors or multiple pharmacies this can also increase the risk of drug interactions since you and your health providers need to be aware of all the medicines you take to check for drug interactions.
  • Older Age. Not only does the number of medicines used increase with age, but there are also age-related physiological changes that affect how well the body handles medicines.
  • Your genetics and other conditions. Some people metabolize medicines faster or slower than other people with the result being a lower or higher concentration in the body of certain medicines, such as tamoxifen, warfarin or clopidogrel.
  • Medicines with narrow therapeutic range. This means that medicines, such as warfarin or phenytoin, need to be exactly dosed to achieve maximum benefits and minimal side effects.

How Can You Prevent Harmful Drug Interactions?

  • Avoid drug interactions by making sure you know which medicines, vitamins, foods, and herbal products can interact with the drugs you’re taking.   Ask your doctor and pharmacist questions.
  • Always get and follow instructions on how to take your medicines and what to avoid while taking them.  Credible web resources exist for learning more about your medicines.
  • Provide your doctor and pharmacist with a complete list of your medicines, including over-the-counter and herbal products. This allows them to check for any potential drug interactions. And stick with one pharmacy if possible. This way your pharmacist can check for drug interactions when filling your prescription.

– Pharmacist Andy