If you're like most folks, remembering that daily dose of cholesterol medication -- or that heart pill or blood pressure drug -- is often easier when you take it with a meal.

However, the truth is what you eat at one of those meals could have some detrimental effects on how a medication works in your body.

One of the most dangerous combinations involves grapefruit, a breakfast staple for many.

"Grapefruit juice influences the production of liver enzymes, which can affect the way certain drugs are metabolized by the body," says Michael Coyne, a registered pharmacist and associate vice president of pharmacy at Staten Island University Hospital in New York City.

This can cause some drugs to end up in the bloodstream in a higher concentration than you are prescribed, Coyne explains. With other drugs, it can inhibit concentration so you don't get the level of treatment you need.

Medications most likely to be affected by grapefruit juice, he says, include antihistamines for allergies, benzodiazepines for anxiety, calcium-channel blockers for hypertension, and statin drugs for cholesterol. Other research has shown reactions may occur with the medicines Viagra, Singulair and Aricept.

If you're wondering whether all citrus juices have the same effect, the answer is no.

"This is a reaction unique to grapefruit juice, so other fruits and juices are safe to consume with these medications," says Maudene Nelson, a registered dietician and nutritionist at Columbia Presbyterian Medical Center in Manhattan.

Another breakfast drink you might not want to mix with your medicines is coffee -- the culprit being caffeine.

In addition to causing gastric upsets that can influence how you feel after taking certain medications, Coyne says caffeine has some potential to affect the way some drugs are metabolized, altering the rate at which the medicine gets into your bloodstream.

Nelson says caffeine-rich drinks can also increase nervousness, and thereby decrease the effectiveness of any drug you might be taking to calm you down.

According to the U.S. Food and Drug Administration (FDA), the medicines most likely to be affected by caffeine include certain bronchodilators for asthma, antibiotics known as quinolones, (drugs like Cipro), and anti-anxiety medications such as Valium, Ativan and Xanax.

In addition, the FDA warns the common bronchodilator, theophylline, can also be affected by high-fat meals, which can increase the amount of the drug in your body, or high carbohydrate meals, which can decrease the drug's levels in your system.

Foods can also affect other asthma medications, depending on the dose form you take -- such as regular release, sustained release or sprinkles. Experts say you should check with your pharmacist, and follow all directions provided with your prescription.

However, the breakfast table is not the only place where folks have to be wary of what they eat. Any desserts that contain licorice can have a powerful impact on blood pressure medication.

"The effects of licorice were established well over 20 years ago, including the ability to raise blood pressure, so it should never be eaten if you are taking medication for hypertension," Nelson says.

Most licorice sold in American supermarkets won't harm you because it usually features synthetic ingredients, or licorice flavoring, Nelson says. Ironically, the licorice you buy in a health food store -- or those imported from Europe -- often contain real licorice. Just a few pieces is enough to cause blood pressure patients harm, she notes.

Another food-drug interaction that may take you by surprise: blood thinners such as Coumadin could be affected by large amounts of otherwise healthy foods such as broccoli. The key factor here is vitamin K, which helps blood clot, Coyne says.

"Obviously if you are taking a medicine to keep your blood from clotting, the last thing you want to do is eat a lot of foods containing the blood-clotting nutrient vitamin K," Coyne says. This includes not only broccoli, but also spinach, brussels sprout and cauliflower.

If you just can't live without these foods, eat the same amount every week and let your doctor know, so your medication can be adjusted.

Finally, among the most dangerous of all beverage-drug interactions is, of course, alcohol, which can dramatically alter how a number of medications act in your body.

"This is particularly true of any drug which affects the central nervous system, which is where alcohol does its work -- drugs such as antidepressants, anti-anxiety agents or sedatives," Nelson says. Other drugs affected by alcohol can include blood pressure medications, cholesterol-lowering drugs and certain heart medications.

"If you have a question about a food or drug interaction, check with your pharmacist and always read the literature that comes from the pharmacy with your medication, and obey all precautions," Coyne says.

What To Do

For more information on food-drug interactions, including a complete listing of the most common drugs and the foods you should avoid, visit New Mexico State University's College of Agriculture and Food Economics.

You can visit the FDA for a terrific brochure on food and drug interactions.

Reference Source 101