Grapefruit juice is one of the healthiest foods around, right?

A cup of unsweetened white grapefruit juice has only 100 calories, no fat, more than 100% of the recommended daily amount of vitamin C, and it's got a zingy taste that can really get you moving in the morning.

However, grapefruit juice (including the juice found in your morning grapefruit half) can interact with certain medications, leading to potentially serious consequences.

Which medications does grapefruit juice interact with?

Grapefruit juice can interact with many different drugs that people take to maintain their health. If you eat grapefruit or drink grapefruit juice, you should ask your prescribing health care provider and pharmacist about any drugs that you're currently taking and ask again whether new drugs interact with grapefruit juice. The list below contains some of the drugs that interact with grapefruit juice. This is not a complete list, so if you're a grapefruit fan, check with your doctor before starting any medication.

* Valium (diazepam): This drug is used to treat certain seizure disorders and anxiety.

* Norvasc (amlodipine): This is one of the drugs called a "calcium channel blocker." It is used to treat angina (chest pain related to malfunctioning arteries around the heart). Grapefruit juice interacts with many of the calcium channel blockers

* Pravachol (pravastatin): Like several of the "statin" drugs used to lower cholesterol, grapefruit juice can change the effectiveness of this product

* Cordarone (Amiodarone): This drug is used to treat "arrhythmias" - to correct irregular heart beat patterns.

What Are The Symptoms of These Interactions?

Use of any of these drugs while taking grapefruit juice can lead to serious complications. For example, the following have been observed in the interaction of each of the drugs above with grapefruit juice:

* Valium (diazepam): Grapefruit juice can cause you to feel sedated and might make it harder for you to control your muscular movements; driving can be dangerous

* Norvasc (amlodipine): Grapefruit interacts with several of the calcium channel blockers to provide a very fast heartrate ("tachycardia") and/or a drop in blood pressure to below safe levels ("hypotension."

* Pravachol (pravastatin): The statin drugs can interact with grapefruit juice to cause muscle toxicities, symptoms of which include muscle weakness, aches and shaking

* Cordarone (Amiodarone): Ironically, mixing this drug with grapefruit juice can cause an increase in the very condition it is intended to treat - arrhythmias

What Causes These Potentially Dangerous Interactions?

How can something as seemingly harmless as grapefruit juice affect the medications you take? It has to do with a special enzyme in your intestines and liver that help you absorb many oral drugs and then excrete them when you're done with the drug.

When a physician prescribes a specific dose of drug (for example, one pill of 50 mg), she works on the assumption that given the size of your body, you will absorb the drug into your body at a certain rate and excrete it at a certain rate. Enzymes in your gastrointestinal (or GI) tract bring food and oral medications into your body. Grapefruit juice seems to affect both the rate of the drug coming into your body and how quickly it is removed. The end result can be an overdose of the drug) even if you're taking the correct dosage for your size.

What Can I Do To Avoid Dangerous Drug Interactions?

If you are on medications that interact with grapefruit juices, avoid eating grapefruit or drinking grapefruit juice. Spacing out the drugs and the juice (for example, taking your medication at night and having grapefruit for breakfast) will NOT solve the problem; the grapefruit juice effect remains even after you've stopped having it. If you like the health benefits of grapefruit, or just miss that morning zing, think about moving to other fruits such as tomatoes (a single can has just 41 calories and more than 70% of the vitamin C for the day) or oranges.