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Avoiding Food and Drug Interactions Linda B. Bobroff Modern medicine has given us many useful drugs that not only prolong and save lives, but improve the quality of our lives. The beneficial effects of the drugs we take can be affected by the foods in our diet. These food and drug Interactions can have dramatic, even dangerous, effects on the way our bodies react to drugs. The purpose of this fact sheet is to present the most common food and drug interactions, and to help you work with your health professional to see that you get the best results from the drugs that you must take. Basic Types of Interactions There are three major types of food and drug interactions: Some drugs interfere with the absorption, excretion or use in the body of one or more nutrients. Certain foods may affect (increase or decrease) the absorption of a drug into the body. Usually, foods and beverages interfere with drug absorption. Certain foods may alter the chemical actions of a drug so that it loses its therapeutic effect on the body. Some reactions can be dangerous and in rare cases can lead to death. The extent of the effects of any food and drug interaction can vary. Potential effects depend on the dose and the form in which the drug is taken (pill, liquid, etc.). It also will vary with the individual's age, sex, body weight, nutritional status, and specific medical condition. The number of potential food and drug interactions is almost limitless. Interaction problems most often occur with the use of diuretics, oral antibiotics, anticoagulant (blood-thinning) drugs, anti-hypertensive drugs, thyroid and sodium compounds, and alcohol. Drug Effects on Nutritional Status Drugs can affect nutritional status in a number of ways: by enhancing excretion of certain nutrients, by interfering with nutrient absorption, or by decreasing the body's ability to change nutrients into usable forms. These effects are gradual so that the effects will be greater in persons taking drugs over a period of time. For these people, vitamin and mineral deficiencies may result. Here are some examples of drug effects on nutrients in the body: Abuse of antacids can lead to phosphate deple- tion. This can lead to a vitamin D deficiency in severe cases. Some patients have developed osteomalacia or softening of the bones due to loss of calcium because of a vitamin D deficiency. The excessive use of diuretics ("water pills") may result in the loss of electrolytes, mainly potassium This may put people with heart problems at higher risk for serious heart rhythm problems. In heart patients taking digitalis as well as a diuretic, potassium loss can make the heart more sensitive to the drug. People taking diuretics regularly should eat foods which are good sources of potassium: tomatoes, tomato juice, oranges, orange juice, cantaloupes, bananas, raisins, prunes, potatoes, sweet potatoes and winter squash. Women who take oral contraceptives over a long period of time may develop folacin and vitamin C deficiencies if their diets are inadequate in these nutrients. The best sources of folacin are spinach and other greens, asparagus, broccoli and lima beans. Excellent vitamin C sources include oranges, grapefruits, lemons and limes, strawberries, tomatoes, potatoes, cabbage and green peppers. Anticonvulsant drugs, prescribed to prevent seizures, can lead to vitamin D and folacin deficiencies. Vitamin D is found in enriched milk. The use of vitamin supplements by patients taking these drugs should be medically monitored. The antihypertension drug hydralazine can deplete the body's supply of vitamin B6. This vitamin is widely distributed in foods. Some good sources are chicken, fish, liver, whole grain breads and cereals, egg yolks, bananas and potatoes. Several drugs, including colchicine (used to treat acute gout), oral antidiabetic agents, and the antibiotic neomycin can impair absorption of vitamin B12. Since most Americans have good vitamin B12 stores in their livers, only long-term use of these drugs is likely to cause a deficiency. Persons who do not eat any animal products (vegans) may have poorer vitamin B12 status and may be at greater risk for a deficiency when taking one of these drugs. Food Effects on Drug Absorption The calcium in milk and milk products such as yogurt and cheese decreases the absorption of certain antibiotics, including tetracycline. These foods should not be eaten at the same time this drug is taken, so that the full dosage of the drug is available for adequate treatment of the infection. Ascorbic acid-containing juices such as orange and grapefruit juices enhance absorption of iron supplements. It is recommended that if you take an iron supplement you should take it with this type of beverage, if possible. In general, it is not recommended that you take drugs with soda pop or high acid fruit or vegetable juices. These beverages can cause excess stomach acidity which can dissolve some drugs before they reach the intestine. Since drugs are mostly absorbed into the body in the intestines, this will decrease the amount of drug that can get into your body. Check with your doctor before taking drugs with these types of beverages. Sometimes certain foods can speed up absorption of a drug. For example, fatty foods increase absorption of griseofulvin, a drug used to treat fungus infections. Food Effects on Drug Utilization Liver and green leafy vegetables can decrease the effect of anticoagulants (bloodthinning drugs). These foods contain vitamin K which helps promote blood clotting. On the other hand, aspirin and aspirin-containing compounds can enhance the effect of the blood-thinning drug and promote excessive bleeding. Aspirin should only be used on the advice of your doctor if you are taking anticoagulants. One of the most hazardous food and drug inter- actions is that between monoamine oxidase (MAO) inhibitors and aged or fermented foods. MAO inhibitors are used to treat depression and high blood pressure. They decrease the metabo- lism in the body of compounds called monoa- mines. MAO inhibitors can react with a substance called tyramine (a monoamine) in foods such as aged cheese, Chianti wine, chicken livers, pickled herring, fava beans and others. As a result blood pressure can rise to dangerous levels causing severe headaches, brain hemorrhage and, in extreme cases, death. Natural licorice contains a substance which can increase blood pressure when eaten in large amounts. Long-term use of licorice and licorice-flavored candy or drugs can counteract the effect of high blood pressure medication. Potential Effects of Sodium and Alcohol People on sodium-restricted diets usually are advised not to add extra salt to their food and to avoid foods naturally high in sodium. They may not know that some prescription and over-the-counter drugs can add significantly to a total day's sodium intake. For a person who is following a 2-gram, sodium-restricted diet, drugs can contain almost onehalf of the total daily allowance. Check with your pharmacist to see if the prescription and over-the-counter drugs you are taking contain sodium. Alcohol should be thought of as a drug. Even small amounts of alcohol are known to interact with many drugs, including certain antibiotics and allergy medicines, blood thinners, and sleeping pills. According to the FDA Drug Bulletin listing of the l00 most frequently prescribed drugs, more than half contain at least one ingredient known to interact adversely with alcohol. The medical toll for alcohol-related interactions is high, including an estimated 2,500 deaths and 47,000 emergency room admissions each year. The chart on the previous page can be used as a guide to assist you in preventing food and drug interactions for some of the most commonly used drugs. If a drug you are taking is not included in the list, check with your physician or pharmacist. Some Final Guidelines to Help You Use Drugs Wisely By now you are aware that the interaction of foods and drugs is a complex problem. Researchers cannot always predict whether a new drug will react with a food or if a drug that's been In use for some time will react with a new food. And you, as the consumer, cannot be expected to know everything about the drug. Then, what can you do to get the greatest benefit from drugs with the least risk? The following guidelines will assist you in preventing problems and getting the most from the medicines that you must take (also see Table 1): When your doctor prescribes a medicine, be sure to mention every other drug that you take, even on an occasional basis - including alcohol and over-the-counter agents such as aspirin, antacids, and laxatives. If you don't know the amount and types of drugs you are taking, take the bottles with you when you visit your doctor. Keep in your wallet a list of all drugs that you are taking. Be sure you understand when and how the product should be taken and then follow directions (for example, with meals, before meals, or after meals). Your pharmacist should have labels that can be pasted on the bottle to remind you when and how the drug should be taken. Tell your doctor about any changes or ill effects you have after taking the drug and any unusual symptoms that occur after eating certain foods. Use the telephone. Don't wait until your next visit. Taking drugs with a full glass of water is generally the safest way and in many cases it may help prevent irritation of the stomach lining. If you take any drug, don't use alcohol without checking with your doctor first to see if it will be safe. If you have been taking a drug for a long time, ask your doctor if you should be concerned about any vitamin or mineral deficiencies. When buying any over-the-counter medicine, be sure to read the label and the package insert for directions and warnings. If in doubt about the product, ask your pharmacist. Finally, use the least number of drugs possible and take them as directed to reduce your chances of developing a drug/drug or food/drug interaction. Selected References FDA Drug Bulletin, Department of Health and Human Services, Washington, D.C., June, 1979. Lehmann, P. (1984) Food and drug interactions. FDA Consumer. September 1984. Lieber, C.S. (1983) Alcohol-nutrition interaction. Contemporary Nutr. 8(12):1-2. (General Mills). Roe, D.A. (1985) Therapeutic effects of drug nutrient interactions in the elderly. J. of Am Dietet. Assoc. 85:174-181. Roe, D.A. (1984) Nutrient and drug interactions. In: Present Knowledge in Nutrition, 5th edition. Washington, D.C.: The Nutrition Foundation, pp. 797-818. For more information about food, nutrition and health, contact your County Extension Home Economist. Table 1. Guide to Food and Drug Interactions <TD>If You Take It's Wise to Avoid Antibiotics: Erythromycin antibiotics:* E.E.S.-400 E-Mycin Erythromycin Ilosone Penicillin antibiotics:* Penicillin V-cillin-K Pen-Vee K Robicillin-V-K Because Acidic foods: Caffeine Citrus fruits Cola drinks Vinegar Fruit juices Pickles Tomatoes These antibodies can be destroyed in the increased stomach acidity caused by these foods. Acidic foods: See above. These antibiotics can be destroyed in the increased stomach acidity caused by these foods. Although calcium-rich foods help ease the digestion that often accompanies tetracycline intake, they also reduce effectiveness. This can allow an infection to go unchecked. If the infection is severe, there can be serious long-term effects, including death. Tetracycline antibiotics:* Achromycin-V Tetracycline Vibramycin Sumycin Calcium-rich foods: Almonds Buttermilk All cheese Pizza Yogurt Cream Ice cream Milk Waffles Foods containing Viatmin K: Beef liver Brussel sprouts Cabbage Oils Chinese cabbage Kale Ruggola Spinach Tyramine-rich foods: Aged cheese** Anticoagulants (to thin blood)* Coumadin Dicumarol Panwarfarin Phenindione Vitamin K promotes blood clotting. Its addition to the body counteracts the bloodthinning effect of anticoagulant drugs. MAO Inhibitors (Antidepressants):* Tyramine (found in these foods) in combination with Marplan Parnate Nardil Chicken liver Cola drinks Canned figs Bananas Beer Broad beans Caffeine Yeast extract Aged meat Chocolate Anchovies Avocados Mushrooms Pickled herring Raisins Sausages: (pepperoni, liverwurst, etc.) Sour cream Soy sauce Wine: Chianti sherry **Particularly Brie, Camembert, Cheddar, Emmenthaler, gruyere, processed American and Stilton Natural licorice: (most licorice in this country is artificial, and not harmful, but imported licorice candy and flavoring from Europe is often natural.) **In addition to natural licorice, avoid tyramine-rich foods listed for Antidepressants, above. Monosodium glutamate (MSG): Often used in seasoned salts, meat tenderizers, frozen vegetables, and Oriental cuisine. **In addition, avoid natural licorice, listed for Antihypertensives these drugs can produce severe headache, palpitations, nausea, vomiting and elevated blood pressure. Potentially lethal strokes and heart attacks have been documented. Antihypertensives<BR< (for high blood pressure):* Calan-S.R. Capoten Inderal Lopressor Ser-Ap-Es Vasotec A substance contained in natural licorice root causes salt and water retention that can lead to elevated blood pressure. Diuretics:* **Aldactone **Hydrodiuril **Lasix HCTZ Monosodium glutamate and diuretics both act to remove excess water from body tissue. In combination they may deplete essential quantities of water-soluble vitamins (C and Bcomplex) and minerals (sodium and potassium). Levodopa(L-Dopa) (for treating Parkinson's disease): Bendopa Dopar Larodopa Sinemet Thyroid preparations: Choloxin Levothroid Synthroid Tapazole Thieuracil Thyrolar Beef and pork liver Wheat germ Yeast Other foods or vitamin supplements rich in vitamin B6 A high protein diet Brussel sprouts Cabbage Cauliflower Kale Mustard greens Rutabaga Soybeans Turnips Iodized salt Vitamin B6 counteracts the activity of L-Dopa in relieving the symptoms of Parkinson's disease. Excessive dietary protein can prevent L-Dopa from reaching the brain. Substance contained in these foods can interfere with thyroid function. They can lead to goiter, a sever metabolic-deficiency disease. * Only a few representative example of these drugs are included. If you are not sure about the type of drug you are taking, speak to your doctor or pharmacist. 1. 2. This document is published by the Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: Revised 1988. Linda Bobroff, Ph.D., Assistant Professor, Extension Foods and Nutrition Specialist, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
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