Preventing harm from drug interactions: consumers can play an important Role

Our colleagues at SafeMedicationUse.ca received a report from a consumer who was given two medicines that are known to interact with each other. This type of problem is known as a drug interaction. A drug interaction occurs when the actions of one medicine affect the actions of another medicine.

The consumer had received a prescription for tamoxifen from a cancer specialist. Tamoxifen is a medicine that is used to treat certain types of breast cancer. Later, the consumer's family doctor prescribed duloxetine (brand name Cymbalta) to treat depression. Duloxetine can reduce the effectiveness of tamoxifen. The consumer took both of these medicines for several months before finding out about the drug interaction during a follow-up visit with the cancer specialist. The cancer specialist told the consumer to stop taking the tamoxifen and prescribed a different breast cancer medicine that does not interact with duloxetine.

Drug interactions can occur with many types of medicines, including over-the-counter and natural or herbal medicines, as well as prescription medicines. Some medicines may also interact with specific foods or alcohol. Drug interactions can be harmful. Some drug interactions require that a different medicine be prescribed, as in the example described here. On the other hand, not all drug interactions mean that you have to stop taking the medicines that interact. Sometimes, you can keep taking the medicines, but a different dose will be prescribed. Sometimes the potential drug interaction will be managed with monitoring by you and your healthcare provider. This monitoring depends on the medicines involved, but may include more frequent assessments to identify if you are experiencing a side effect or if your medicines are working as intended.

Consumers can play an important role in preventing harm from unrecognized drug interactions. Here are some tips:

• Use the same pharmacy to fill all your prescriptions. Be sure to tell your pharmacist about any over-the-counter, natural, or herbal medicines that you take. This will allow your pharmacist to check for all potential drug interactions.
• Keep a list of all your medicines and how you use them. Take the list with you every time you visit a healthcare provider. Show the list of medicines to your healthcare providers, and ask them to help you update the list if they make changes to your medicines. This is particularly important if more than one healthcare provider is prescribing medicines for you.
• Listen to what the pharmacist tells you about your medicine. Ask the pharmacist any questions you may have about what you are taking, including whether it might interact with other medicines. Always read any printed material that you receive with your medicine, as this often includes information about medicines that may interact, as well as information about possible side effects.
• Take note of the labels on the containers for your prescription medicines, as provided by your pharmacy. These can remind you of potential drug interactions. The following are just some examples:
• When selecting over-the-counter, natural, or herbal medicines, carefully read the information on the label. Ask your pharmacist for assistance with selecting these medicines. Be sure to discuss the other medicines you are taking and ask whether the product may interact with them.
• Although websites for checking drug interactions are available, it is important to seek advice from your own healthcare provider before making any changes to your medicines.

With permission, this information was reprinted from material originally published on http://www.safemedicationuse.ca/