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Medication interactions

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 2 minutes read

Medication interactions are the situation where two or more medications interfere with each other. Interactions range from harmless to extremely dangerous; however, fear not because doctors and pharmacists are here to keep you safe. There are too many combinations of medications to list all potential interactions, but certain groups of medications are known to have lots of interactions.

When you are prescribed multiple medications, your doctor and pharmacist will check to ensure it is safe to take them together. It is best to get all your prescriptions dispensed from the same pharmacy. That way your pharmacist will be aware of all your prescribed medications.

How do interactions occur, and what are the effects?

Common interactions relate to how medications are removed from your body. Most medications are broken down by liver enzymes and then eliminated by the kidneys in your urine.

Some medications can affect how these enzymes work and lead to problems. For example, erythromycin (an antibiotic) inhibits an enzyme that breaks down simvastatin (a medication used to lower your cholesterol). This leads to increased simvastatin in your body and an increased risk of developing side effects. For this reason, simvastatin and erythromycin should not be taken together.

Also, some medications like antacids can reduce the absorption of other medications into your body through your gastrointestinal system, thereby reducing the effectiveness of the medication. Separating the two medications can reduce this potential interaction.

Other medications interact because they cause the same side effects. For example, many medications, such as antidepressants, sedating antihistamines, and opioid painkillers, can cause drowsiness.

Beneficial interactions

Not all interactions are undesirable, and some can be beneficial. These interactions can occur when different medications produce the same therapeutic effect. For example, many people with high blood pressure require several medications to lower their blood pressure.

Can medications interact with food and drink?

Some medications can interact with food and drink. Food can decrease the absorption of some medications, such as the antibiotics penicillin and tetracycline. Therefore, they should be taken on an empty stomach.

Other medications like warfarin can interact with specific foods, such as foods high in vitamin K. If you take warfarin, you need to consume a similar amount of these foods each day, as they affect the dosage of warfarin you need to take.

Drinks that can interact with medications include alcohol, grapefruit juice, and cranberry juice.

Buying medications without a prescription

You must be careful when buying medications without a prescription, as they may interact with your prescribed medications. They may also interact with each other if you buy multiple medications. As a general rule, you should speak with your doctor or pharmacist before using any medications together to ensure it is safe. This also applies to vitamins, supplements, and herbal medicines.

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Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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