Supplements and Drugs Don't Always Mix
In last week's column, I wrote how calcium interferes with the absorption of iron. This is an example of supplement interaction and it doesn't just happen between competing minerals. It can also occur between vitamins/minerals, herbs, and other drugs.
These days, it is not uncommon for people to take a combination of supplements ranging from vitamins and minerals to herbs to hormones like melatonin. "Poly-pharmacy" is the term used by the American Council on Science and Health (ACHS) to describe the practice of taking many medications and supplements. The non-profit consumer education organization warns that there is a risk of an adverse interaction between supplements and prescription or over-the-counter drugs.
The ACHS lists down several possible ways that an interaction can occur. First, a drug and a supplement can have similar actions so when you take both at the same time, the effect is magnified. For example, vitamin E and anti-coagulation medication both thin the blood. Taking both may cause internal bleeding.
Second, a supplement may counteract the effect of a drug. In other words, the supplement and the drug have opposing functions. In the example used by the ACHS, zinc (which stimulates the immune system) can interfere with drugs that are designed to suppress the immune system like corticosteroids.
A third type of interaction happens when a supplement affects the absorption of the drug. If calcium is taken at the same time as tetracycline (a type of antibiotic), less of the drug may be absorbed. As a result, according to the ACHS, the drug won't be as effective as it should be.
The last type of interaction mentioned by the ACHS is when a supplement affects the way the body breaks down a drug. "For example, the herb St. John's wort increases the activity of an enzyme that breaks down some drugs used in the treatment of heart disease, cancer, or AIDS as well as drugs used to prevent the rejection of organ transplants. If a patient who is taking one of these drugs also takes St. John's wort, the drug may be broken down more quickly than usual, and it won't be fully effective".
It isn't just supplements that can interfere with your medications. Some types of food can also have a significant effect, sometimes even a fatal one.
A chemical called tyramine, which is found in some beers, wines, cheese, and sausages can cause a dangerous rise in blood pressure in people taking a specific type of anti-depressant known as MAO inhibitors.
Another food item that can cause major problems is grapefruit. It contains a still unidentified substance that affects the way certain drugs are broken down by the body making the concentration of the drugs in the blood either higher or lower than normal. Although grapefruit juice does not have this effect on all drugs (it usually affects drugs for lowering cholesterol and blood pressure, certain antihistamines, and anti-depressants), expert say it is best to avoid taking any kind of medication with grapefruit juice. Other citrus juices are okay.
The other substance that should be avoided when taking medication is alcohol. It usually interacts (makes the drug more concentrated, less effective or causes side effects like dizziness and nausea) with antibiotics, anti-depressants, anti-coagulants, cardiovascular medication, diabetic medications, antihistamines, sedatives, anti-ulcer, pain relievers, and the list goes on. Like grapefruit juice, alcohol doesn't adversely affect all drugs but it affects so many of them that the wisest thing to do is to totally avoid mixing alcohol with your medication.
Here's a short
list of common supplement-drug interactions. For more detailed information,
· http://www.acsh.org/publications/story/drug_suppl/ (supplement-drug interaction)
· http://www.nclnet.org/fooddruord.html (grapefruit-drug interactions)
· http://www.niaaa.nih.gov/publications/aa27.htm (alcohol-drug interactions)
In general, poor
vitamin absorption is the common problem when taken with drugs.
· Tetracyline will deplete the amount of vitamin C in your body while salicylates (like aspirin) decrease the uptake.
· Neomycin can retard the absorption of vitamin A and beta-carotene while tetracycline can cause high blood pressure when combined with vitamin A and beta-carotene.
· Oral contraceptives increase the requirement for vitamin B-6.
· Aspirin competes with folic acid while barbiturates will cause malabsorption of the vitamin.
Vitamin E should not be taken with anti-coagulants or blood thinners, omega-3 fatty acids (fish oil supplements), and corticosteroids because of the increased blood thinning effect.
Calcium can interfere with the absorption of tetracycline and thyroid hormones.
High doses of vitamin C can interfere with tests for blood in the stool.
Alcohol can increase the sedative effect of chamomile, kava, and valerian.
The ACHS has three additional warnings that are worth mentioning:
"The extent to which St. John's wort interacts with medications is only beginning to be understood. ACSH recommends that anyone who is taking any crucially important medication should not use this herb unless the physician who prescribed the drug has specifically approved its use.
"More food and drug interactions have been reported for Coumadin (a type of blood thinner) than for any other medication. Patients taking Coumadin should not start or stop taking any other medications or alternative therapies or make any substantial changes in their eating habits without consulting their physicians.
"Because there is a potential for extremely serious interactions between monoamine oxidase (MAO) inhibitors and a variety of food components, dietary supplements, and other drugs, anyone who is taking this type of medication should scrupulously follow all of the dietary and other instructions provided by the physician who prescribed the drug."
The phenomenon of "poly-pharmacy" indicates how important it is to give your doctor a complete list of all the supplements and other medication that you are currently taking whenever you are prescribed new medication. Sometimes your doctor will tell you take the supplement and the drug two hours apart, take them separately in the morning and evening, or will tell you to stop taking the supplement while you are taking the medication.
In addition to
being honest with your doctor, get as much information as you can on the possible
interactions between your supplements and medication. It's always best to be
pro-active about your health.
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