Do you regularly take alternative or complementary medications such as vitamins and minerals, herbal treatments or essential oils? If so, you should tell your pharmacist. Such products – no matter how natural – could interact with your prescribed medicine even if you’ve not had any previous problems.

Sideeffects may occur when mixing medications. The drugs suggested by your doctor could prove less effectiveor potentially stronger in combination with other substances. In either case, your treatment and possibly your health might be negatively affected. In this blog, we’ll look at some interactions to note.

Complementary medicine side effects

Natural treatments have long been used to treat a range of ailments. However, the active compounds contained in these treatments can react with a range of prescription medications. Here is a guide to some of the most common combinations to watch out for. Notify your pharmacist if you think there may be an issue.

Ginseng Chemotherapy, HIV medication, blood-pressure and cholesterol-lowering medication, antidepressants Decreased effect of medicine
Ginkgo Warfarin (anticoagulant) Increased risk of bleeding
St. John’s Wort Blood-pressure HIV, depression, cancer and anxiety medications. Also anaesthetics, oral contraceptives Decreased effect of medicine
Echinacea Antipsychotic and antidepressant medications. Also etoposide chemotherapy treatment Increased effect or risk of side-effects
Feverfew Omeprazole, lansoprazole, pantoprazole, diazepam, carisoprodol, nelfinavir and others. Decrease in effectiveness of the liver breaking down the medication
Chamomile Central nervous system depressants Increased effect of medicine
Evening primrose Warfarin (anticoagulant) Increased effect of medicine
Fish oil supplements Antihypertensive drugs
Warfarin (anticoagulant)
Lowered blood pressure
Increased bleeding risk
Garlic supplements Oral contraceptives
Warfarin (anticoagulant)
Decreased effect of medicine
Increased bleeding risk
Hawthorn Betablockers Increased effect of medicine
Senna Diuretics Increased effect of medicine
Valerian Alprazolam and Central nervous system depressants Increased effect of medicine
Vitamin E Warfarin (anticoagulant)
Increased effect of medicine
Decreased effect of medicine


When talking to your pharmacist, be sure to provide the following information on your complementary medicines:

  • The name of the supplement you are taking
  • How often or for how long you have taken the medicine
  • The amount of active ingredients in each dose – take the medicine with you if possible
  • Why you are taking this treatment
  • Any effects or side-effects you have experienced with the complementary medicine

Your pharmacist may advise you to stop taking your alternative choice temporarily. This will be for the benefit of your health and for a quicker recovery. Do not assume that health professionals are automatically against “rival” treatments – it’s just that they have a deeper knowledge of the body’s functions. Feel free to ask questions!

It is especially important to speak with your pharmacist if you are:

  • Pregnant or intending to become pregnant
  • Breastfeeding
  • Scheduled for an operation or other medical procedure
  • A child
  • Over the age of 65
  • Currently or previously diagnosed with a disease

Food-drug interactions with medications

Many patients are surprised to find out that some common foods can react with prescribed medicines. Here’s a list to be aware of:

Dairy: milk, yoghurt, cheese Antibiotics
Iron supplements
Inhibited absorption
Pickled, cured and fermented foods or aged cheese Monoamine oxidase inhibitors (MAIOIs) and Parkinson’s medication Increased blood pressure
Kale, spinach and other vitamin K-rich foods Warfarin (anticoagulant) Contrary effect to the drug
Alcohol Stimulants
Masked level of intoxication
Liver toxicity
Severe vomiting
Grapefruit Statins Increased effect of medicine
Licorice Aldactone (diuretic) Renders drug ineffective
Cranberry Warfarin (anticoagulant) Increased effect of medicine
Ginger Warfarin (anticoagulant) Increased bleeding risk
Any food Hypothyroid medications Medicine requires an empty stomach


Again, talk to your pharmacist if you eat a lot of one kind of food. If you are advised to avoid certain foods while taking prescribed medication, take the guidance seriously because negative interactions could prolong your recovery or harm your health.

At Doctors Express, we have the benefit of having all medications at one location in our on-site pharmacy, so a qualified pharmacist is able review all medications and talk to you. Please tell us about any other treatments you are taking and be assured that we will give you the best advice for your health.

For more information about our pharmacy, visit the website.

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