Over-the-counter medicines that clash with chronic tablets

Walking down the pharmacy aisle, it’s easy to assume that anything you can buy without a prescription must be harmless. An anti-inflammatory for a sore knee, a flu remedy for a cold, a herbal supplement for more energy.

But “over the counter” doesn’t mean “safe with everything”.

If you already take prescription medicine for blood pressure, cholesterol, diabetes or your heart, some everyday products can interfere with it.

Common clashes worth knowing about

• Anti-inflammatory painkillers and blood pressure. Painkillers such as ibuprofen and diclofenac can make your body hold on to salt and water. This can push your blood pressure up and work against your blood pressure medicine. They can also be hard on the kidneys, especially alongside some heart and blood pressure medicines.
• Herbal products and blood thinners. “Natural” doesn’t mean it can’t interact. St John’s wort can make several medicines less effective, including the blood thinner warfarin. Ginkgo can add to the risk of bleeding when taken with blood thinners.
• Flu and cold remedies and heart conditions. Many decongestants work by narrowing blood vessels to clear a blocked nose. They can also raise your blood pressure and heart rate, which matters if you have high blood pressure or a heart condition.

Before you add anything new

Before adding a new tablet, syrup, vitamin or herbal product, check that it works well with what you already take. Tell your doctor and pharmacist about everything you use, including supplements and things you only take now and then.