What combinations of medicines could be a problem when mixed?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)

There are many prescription and over-the-counter (OTC) combinations that should put people on high alert. The rule of thumb is to not introduce any new prescription or OTC medicine, vitamin, or herbal supplement that will interfere with the action of one you are already taking. Anything that can increase, decrease, or cancel the effectiveness of medications; cause a brand new side effect; or get in the way of how the drug is processed in the body can have grave consequences.

Here are just a few bad combinations:

  • OTC pain reducers and prescription blood thinners. Certain anti-inflammatory pain medications called NSAIDs (aspirin, ibuprofen, naproxen) reduce body chemicals called prostaglandins that are involved in pain pathways. But these chemicals also protect the stomach lining. They also tend to add to the anticoagulant power of blood thinners by further reducing platelets, the blood cells involved in clotting. The combo can cause massive gastrointestinal bleeding.
  • OTC calcium supplements and prescription thyroid medication. When taken with prescription thyroid medications, the calcium found in dietary supplements and antacids interferes with the absorption of the thyroid hormone. The combo can cause an inadequate amount of thyroid hormone circulating in the blood.
  • OTC decongestants and prescription diabetes drugs. Decongestants found in cough and cold remedies not only have added sugar, but they raise blood pressure, a common problem for people with diabetes who may also be taking medications to lower high blood pressure. The combo can cause hypertension, high blood sugar, increased stroke risk, and poor glucose control.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.