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Grapefruit juice--felodipine interaction in the elderly
G K Dresser1, D G Bailey, S G Carruthers
1Department of Medicine and Pharmacology and Toxicology, London Health Sciences Centre and University of Western Ontario, Canada.
Clinical Pharmacology and Therapeutics
|August 17, 2000
Summary
Grapefruit juice significantly increases felodipine bioavailability in the elderly, leading to unpredictable drug interactions. Caution is advised for elderly individuals consuming grapefruit juice with felodipine medication.
Area of Science:
- Pharmacology
- Geriatrics
- Drug Interactions
Background:
- Grapefruit juice is known to increase oral bioavailability of many medications.
- The interaction between grapefruit juice and felodipine has not been studied in elderly populations.
Purpose of the Study:
- To assess the pharmacokinetic interaction between grapefruit juice and felodipine in healthy elderly individuals.
- To evaluate the impact on felodipine bioavailability, metabolism, and associated physiological effects.
Main Methods:
- A single-dose and a steady-state study were conducted in elderly participants (70-83 years).
- Participants received felodipine extended-release with either grapefruit juice or water.
- Plasma concentrations, blood pressure, and heart rate were monitored.
Main Results:
- Grapefruit juice increased mean felodipine area under the curve (2.9-fold) and maximum concentration (4.0-fold).
- High interindividual variability in interaction extent was observed.
- Heart rate increased with grapefruit juice, particularly at steady-state.
Conclusions:
- Grapefruit juice causes a significant, unpredictable pharmacokinetic interaction with felodipine in the elderly by reducing presystemic metabolism.
- Elderly individuals should be cautioned against consuming grapefruit juice concurrently with felodipine.