Do Furanocoumarins Mediate the Fexofenadine-grapefruit Juice Interaction?
Status:
Completed
Trial end date:
2011-04-01
Target enrollment:
Participant gender:
Summary
Purpose: Grapefruit juice is one of the most extensively studied dietary/natural substances
shown to interact with a variety of medications. However, unanswered questions remain
regarding the causative ingredients and mechanisms underlying such drug-grapefruit juice
interactions. Compounds in grapefruit juice called furanocoumarins have been established as
major causative ingredients, which act by inhibiting the elimination (metabolism) of drugs,
leading to increased circulating drug concentrations. Increased drug concentrations can in
turn lead to increased drug potency or even toxicity. Grapefruit juice also has been shown,
paradoxically, to decrease circulating concentrations of some drugs, including the
non-sedating antihistamine agent, fexofenadine (Allegra), which undergoes negligible
metabolism. Whether or not furanocoumarins mediate the decrease in fexofenadine
concentrations is unknown. The purpose of the proposed study is to compare the effects of a
"furanocoumarin-free" grapefruit juice with grapefruit juice on circulating concentrations of
fexofenadine.