Spring 2004

Ask the Pharmacist: The Drug-Diet Connection
By Christy Wiebe, Pharm.D.

With an increased emphasis on the growing rate of obesity in America, renewed interest has been focused on eating healthy and losing weight, and it seems that new diet plans are cropping up at an alarming speed. But in their haste to adopt the latest trend, many Americans ignore the good advice to “Consult your physician and pharmacist before beginning any weight loss program.” Changing your eating habits can sometimes affect the way certain medications work. The following is some helpful information regarding drug-food interactions.

Grapefruit Juice - Is it safe?

Grapefruit is another popular diet food that can interact with certain medications. Grapefruit juice is known to block the way that some drugs are metabolized (broken down) in the body and can lead to increased side effects from those drugs. Below is a table of some of the more popular drugs that might be affected by grapefruit juice. The best advice is to avoid taking any medications with grapefruit juice until you have confirmed with your doctor or pharmacist that it is safe. Also, if you increase the amount of grapefruit you eat, or if you already drink grapefruit juice regularly, consult with your physician or pharmacist to make sure that your medications will not interact. Tangelos are related to grapefruit and may also interfere with some medications, but most other citrus fruits (lemons, limes, tangerines, and naturally sweet oranges) are considered safe.
 

Some Drugs that May Interact with Grapefruit Juice
 

Coumadin & vitamin K

Coumadin (warfarin) is a popular blood thinner used in patients with certain cardiovascular conditions like blood clots, arrhythmias, and artificial heart valves. It works by blocking vitamin K—an important part of the natural blood clotting process. However, ingesting excess amounts of foods rich in vitamin K can actually reverse the blood-thinning effect of Coumadin. Foods containing high amounts of vitamin K include green leafy vegetables (spinach, kale, lettuce, brussel sprouts, broccoli, cauliflower, and others), cooked liver, and soy protein products, including tofu. Although these foods are not forbidden for people taking Coumadin, it is very important to be consistent about the amount of such foods that are eaten on a regular basis. If you wish to start a new diet or increase your intake of vitamin K-rich foods while taking Coumadin, consult your physician. Additional monitoring may be necessary while you are changing your eating habits.

Prescription Drug Interactions

A few prescription drugs may interact with foods that are high in potassium like bananas, citrus fruits, and green leafy vegetables. Fortunately, this interaction is relatively uncommon and moderate amounts of potassium-rich foods are generally safe. However, avoid eating large amounts of potassium-rich foods if you take certain blood pressure medications called ACE Inhibitors (e.g. Vasotec (enalapril), Prinivil/Zestril (lisinopril), Accupril (quinapril), Capoten (captopril) and others), or a diuretic called triamterene, or if you are already taking a separate potassium supplement. Also, be careful about using salt substitutes that contain potassium in place of sodium. Too much potassium may result in an irregular heartbeat or heart palpitations. As always, moderation and consistency are the best way to avoid problems.

Three Rules to Remember

Eating healthy is certainly a wise lifestyle change and will help you maintain good health in many ways. If you are concerned about drug-diet interactions, remember three easy rules:
1) Be consistent with the types and amounts of foods that you eat,
2) Be cautious if you choose to change your eating habits or if you start new medications, and
3) Consult your physician and pharmacist about drug-food interactions when making changes to your diet or medications.