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Common Items That Can Affect Your Medication

You may know that some medicines don’t work well together. But what you eat and drink can have an effect on some drugs, too.


I am often asked about whether bioidentical hormones can be used with various types of drug. In particular with HRT, hormonal contraception including the coil, blood pressure and thyroid medications.

Also women with a risk or history of breast or other hormonal cancers ask about using bioidentical hormones alongside drugs such as Tamoxifen.

There is no contraindication with any medication or nutritional supplement, other than those containing synthetic hormone such as the Pill/Coil/HRT. Bioidentical doctors recommend using progesterone alongside cancer drugs such as Tamoxifen to help with the side effects.

It is always best to check first if the cream you want to use will be effective as it will depend on the specific ingredients or combination of the drug or device.

What particular foods will affect your medication?

You may know that some medicines don’t work well together. But what you eat and drink can have an effect on some drugs, too. Before you take a medication for the first time, ask specifically your doctor or pharmacist to see if there’s anything you should stay away from.

1. Grapefruit and general drug use

This citrus fruit changes the way certain cells in your gut take in and move medication through your body and can affect more than 50 drugs. It can make some, like fexofenadine (Allegra) for allergies, less effective and make others too strong, including ones that lower your cholesterol like atorvastatin (Lipitor) and thyroid medications.

However it seems it is the quantity that is the issue. A study by Lilja, Laitinen and Neuronen (Journal of Clinical Pharmacology in 2005) looked at this. They got volunteers to drink 200ml of pure grapefruit juice 3 times a day for two days, then take a dose of T4 (Thyroid medication) with two more 200ml of juice an hour either side of that, and measured various levels.

Their conclusion was that grapefruit juice may ‘slightly delay the absorption of T4, but seems likely to have only a minor effect on its bioavailability – and this with 400-600 ml pure juice.

So if drinking a lot of grapefruit juice, or eating the fruit itself, check with your doctor.

2. Milk and antibiotics

This dairy product can make it harder for your body to process certain antibiotics. Minerals in milk like calcium and magnesium are part of the reason, along with the protein casein.

If you’re taking antibiotics, make sure to find out about the foods or beverages you should stay away from

3. Liquorice and blood pressure

Some people use this as a herbal remedy to help with digestion, and others use it to flavour foods. But glycyrrhizin, a chemical in licorice, can weaken the effect of some drugs, including cyclosporine, used to keep people who’ve had transplants from rejecting their new organs.

However, large and even moderate amounts of black liquorice (57g or around 2oz) can have negative physical effects when eaten daily, especially if you are aged over 40 and have a history of cardiovascular disease or high blood pressure.

4. Chocolate and sleep/anxiety drugs

Dark chocolate in particular can weaken the effects of drugs meant to calm you down or make you sleep, like zolpidem tartrate (Ambien).

It also can boost the power of some stimulant drugs, like methylphenidate (Ritalin). And if you take an MAO inhibitor, used to treat depression, it can make your blood pressure dangerously high.

Like the grapefruit, this will probably depend on the quantity you are eating but personally I find chocolate harder to limit than grapefruit!

5. Iron Supplements and thyroid medication

This can lower the effects of levothyroxine, a medicine that gives you thyroid hormone when your body doesn’t make enough.

If you take this medication and a multivitamin, check to see if the vitamin has iron in it. If you need an iron supplement, ask your doctor about taking it and your medication at different times.

6. Alcohol and heart and blood pressure medications

This makes certain drugs less effective or even useless, including some blood pressure and heart medicines. It also can make others stronger than they should be or cause dangerous side effects.

Always check with your doctor or pharmacist for each medication you are prescribed and its interaction with alcohol.

7. Coffee and antipsychotic drugs and aspirin

It can weaken antipsychotic drugs like lithium and clozapine, but boost the effects — and side effects — of others.

Those include aspirin, epinephrine (used to treat serious allergic reactions), and albuterol (taken by inhaler for breathing problems).

It can also make it harder for your body to take in and use iron.

8. Antihistamines and high blood pressure medication

These help with the sneezing and runny nose caused by allergies, but some of them can make medication for high blood pressure less effective and raise your heart rate.

If you are on BP medication then talk to your doctor about other ways to manage your allergies or look for a way to boost your immune by increasing your intake of garlic. It also acts as a decongestant and helps alleviate minor hay fever symptoms.

It’s also an anti-inflammatory and a good source of quercetin, a natural antihistamine.

9. Anti-Epileptic Drugs (AEDs) and contraceptives

These control seizures in people who have epilepsy. But AEDs can make birth control pills less able to prevent pregnancy, and early research shows they may make other drugs stronger and cause potentially serious side effects.

10. Vitamin K and Warfarin

If you take the drug warfarin — used to treat and prevent blood clots — be aware of how much vitamin K you take in. It can make the blood thinner less effective and put you at higher risk of a dangerous blood clot.

Foods high in vitamin K include broccoli, Brussels sprouts, kale, parsley, and spinach. If these are your favourites then try to eat the same amount every day so the level of warfarin in your blood stays the same.

11. Ginseng and Warfarin and NSAID’s

This can lower the effects of warfarin, too. And it can make you more likely to have internal bleeding if you take the blood thinners heparin or aspirin, as well as nonsteroidal anti-inflammatory drugs like ibuprofen or naproxen.

If you take MAO inhibitors, ginseng can cause headaches, sleep problems, hyperactivity, and nervousness.

12. St. John’s Wort and cholesterol/heart medications

Sometimes used to help people with depression but it can make your liver release enzymes that can weaken some medications.

Those include cholesterol drugs like lovastatin (Altoprev and Mevacor), and digoxin (Lanoxin), used to treat certain heart conditions.

13. Ginkgo Biloba and anti-seizure drugs

Some people use this herb to help with or prevent high blood pressure, dementia, ringing in the ears (tinnitus), and other conditions.

However it can weaken the effect of drugs used to control seizures, including carbamazepine (Carbatrol, Equetro, and Tegretol), and valproic acid (Depakene, Depakote, and Stavzor).

Helpful information:

Only about 50% of medication is taken as it’s prescribed. People often take less than they need, take it at random times, or leave big gaps between doses — all of which can weaken the effects. Make sure you understand your treatment plan and follow your doctor’s instructions.

As bioidentical hormones have no side effects or withdrawal symptoms they can generally be used with all medications other than those containing synthetic hormones. Always check if you have a coil, are on the Pill or HRT to make sure your medication will not be affected as in some circumstances bioidentical hormones can still be used alongside such products.