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Medication interactions

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 3 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 try to keep you safe. There are too many possible combinations of medications to list all potential interactions, but there are certain groups of medications that are known to have lots of interactions.

When you are prescribed multiple medications, your doctor and pharmacist will check to make sure it is safe to take them together. It is best to get all your prescriptions dispensed from the same pharmacy. Therefore, your pharmacist is aware of all the medications you have been prescribed.

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 enzymes in your liver and are then eliminated by your 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 can lead to an increased amount of 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. Therefore, reducing the effectiveness of the medication. Separating the two medications can reduce this effect.

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, 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 drinks. Food can decrease the absorption of some medications, such as the antibiotics phenoxymethylpenicillin and flucloxacillin. 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 need to be careful when buying medications without a prescription, as they may interact with your prescribed medications. If you are buying multiple medications, they may also interact with each other. As a general rule, you should speak with your doctor or pharmacist before using any medications together to make sure it is safe to do so. This also applies to vitamins, supplements, and herbal medicines.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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