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[Excessive terfenadine level due to drinking grapefruit juice]
J N van den Anker1, S N de Wildt
1Afd. Kindergeneeskunde, Academisch Ziekenhuis Rotterdam-Sophia Kinderziekenhuis.
Nederlands Tijdschrift Voor Geneeskunde
|April 29, 1998
Summary
Grapefruit juice significantly increases drug levels in the body by inhibiting intestinal enzymes. This food-drug interaction can lead to dangerous side effects, particularly heart rate disturbances from medications like terfenadine.
Area of Science:
- Pharmacology
- Drug Metabolism
- Drug Interactions
Context:
- Prescribing physicians must consider food-drug interactions alongside drug-drug interactions.
- Grapefruit juice is a common dietary component with known effects on drug bioavailability.
- Certain frequently prescribed medications are susceptible to interactions with grapefruit juice.
Purpose:
- To highlight the clinical significance of grapefruit juice in altering drug pharmacokinetics.
- To explain the mechanism by which grapefruit juice affects drug metabolism.
- To warn about the potential adverse events arising from enhanced drug bioavailability.
Summary:
- Grapefruit juice consumption elevates the systemic bioavailability of drugs, including terfenadine, by inhibiting intestinal cytochrome P450 3A4.
- This inhibition impairs the metabolic degradation of susceptible drugs, leading to increased blood concentrations.
- Elevated terfenadine levels, for example, are associated with an increased risk of cardiac arrhythmias.
Impact:
- Physicians should counsel patients on avoiding grapefruit juice when taking interacting medications.
- The findings underscore the importance of comprehensive patient education regarding potential food-drug interactions.
- Regulatory considerations for over-the-counter availability of implicated drugs may need re-evaluation due to safety concerns.