The Dangers of Grapefruit Juice Interacting with Drugs

A doctor warns of the dangers of grapefruit juice interacting with drugs, includes how the body processes foreign compounds and specific drugs that interact when mixed with common grapefruit juice.


| November/December 2001



There are real dangers of grapefruit juice tnteracting with drugs.

There are real dangers of grapefruit juice tnteracting with drugs.

Photo By Mother Earth Living staff

Learn about the dangers of grapefruit juice interacting with drugs.

Grapefruit Juice Interacting with Drugs

Our bodies have a remarkable ability to process foreign compounds. Consider the massive number of medications that have been introduced in the past fifty years. These pharmaceutical agents have many diverse actions such as treating cancer, menopausal symptoms, infections, inflammation, pain, anxiety, seizures, high blood pressure, and high cholesterol, just to name a few. It’s a wonder that chemicals designed in a laboratory could have such powerful and pervasive biochemical effects on our physiology. And it is perhaps equally wondrous that we manufacture an elaborate set of enzymes that allows us to take drugs in precise doses over extended periods of time without developing intolerable side effects. These enzymes accomplish this feat by metabolizing the drugs so that they can be eliminated from our bloodstream and tissues before they become toxic.

There is only one catch to this elegant garbage disposal system—it is prone to clogging. In modern cultures, human beings typically eat a complex diet that includes a wide variety of foods and spices. In addition, the trend toward medical self-care has led us to consume a growing number of herbal medicines. Foods and herbs contain a vast array of naturally occurring chemicals—too many to count—that are also processed by the very same enzymes that metabolize drugs, hormones, and toxins. This massive influx of chemicals burdens the disposal system, placing it at risk of overloading. As a consequence, the more new drugs we introduce into our bodies, the more likely we are to encounter significant interactions between these drugs, the foods we eat, and botanical medicines.

The Case of Grapefruit Juice and Drugs

A case in point is grapefruit, an extremely popular and nutritious food. Surveys have shown that up to 21 percent of all households in the United States purchase grapefruit juice. For most consumers, this is probably a very good thing—there are substances in grapefruit that appear to help prevent both cancer and heart disease. However, grapefruit juice also has a unique property: It can raise the blood levels of numerous prescription medications. Because grapefruit juice is usually consumed with breakfast—the same time that many people take their medications—this increases the likelihood of a significant effect. Depending on the condition being treated and the relative safety of the drug involved, this interaction could potentially be a problem . . . or, it could also be a benefit.

Almost ten years ago, a medical study was conducted to investigate the effect of alcohol on the absorption of a blood pressure medicine called felodipine. As part of the study, grapefruit juice was added to mask the taste of the alcohol. Much to the investigators’ surprise, it was discovered that the addition of grapefruit juice markedly enhanced the absorption of felodipine and raised its concentration in the bloodstream. In the years that followed, a similar effect was found with numerous other medications, and extensive research was conducted to find out exactly how this interaction occurred.

A central component of the body’s drug detoxification system is a family of enzymes called the cytochrome P450, or CYP450. These enzymes are found throughout the body but are especially concentrated in the liver and the walls of the intestines. The role of these CYP450 enzymes is to alter the chemical structure of a drug (or hormone or toxin) so that it can be more rapidly eliminated. When certain CYP450s are blocked or inhibited, the effect is to slow down the elimination of that substance, thus raising its level in the blood.





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