Double-whammy: Food-drug Interactions Components in Grapefruit and Other Foods May Dramatically Affect Absorption and Metabolism of Therapeutic Drugs

29-year-old man, who had been taking a prescription allergy medication, twice a day, for over a year, drank two glasses of grapefruit juice with his medication and went out to mow the lawn. Suddenly, he became ill, stumbled into his home and collapsed. The coroner found that the man had died of irregular heartbeats caused by drug toxicity. Because of the deadly consequences of this allergy medication interacting with grapefruit juice and other drugs, the allergy medication was pulled off pharmacy shelves. Scientists in industry and in academe are constantly vigilant about drug interactions and now are looking at food-drug interactions with increasing interest. About ten years ago, scientists accidentally discovered and reported the very first grapefruit juice-drug interaction. Doctors Spence, Bailey, and Arnold were studying the interaction between the consumption of alcohol and a drug to lower blood pressure. The investigators wanted to conduct a " blind " study. By disguising the taste of alcohol, the subjects would not know if they were taking the drug with alcohol. A taste-test of every juice in one of the investigator's refrigerators was conducted on a Saturday evening. Double-strength white grapefruit juice (a single dilution of frozen concentrate) was chosen to mask the taste of alcohol. Patients received the drug either with grapefruit juice alone (control) or grapefruit juice with alcohol. After the study subjects took the drug, they showed drug levels in their blood three times higher than predicted. The high drug levels puzzled the investigators. They double-checked that the correct dose was given and that they were measuring the right levels. Since previous studies administered the drug with water instead of grapefruit juice, Bailey took the drug with water and then with grapefruit juice. After taking the drug with juice, his blood concentrations were five-fold greater than with water. He experienced dizziness and redness in the face. The higher drug levels were attributed to an interaction with grapefruit juice. Over the last ten years, at least 40 drugs have been examined for an interaction with grapefruit juice, but scientists are only beginning to understand how grapefruit juice affects the body. What is the cause of the grapefruit juice-drug interaction? Basic research at institutions including the University of Washington are helping to shed light on the phenomenon. It appears that grapefruit juice changes how much drug gets into the body. Certain compounds in grapefruit juice act on the small intestine where …