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Grapefruit juice increases oral nimodipine bioavailability
U Fuhr1, A Maier-Brüggemann, H Blume
1Institute for Pharmacology, Clinical Pharmacology, Universität zu Köln, Germany.
Summary
Grapefruit juice significantly increased the bioavailability of nimodipine, a dihydropyridine calcium channel blocker. This interaction means nimodipine should not be taken with grapefruit juice to avoid potential adverse effects.
Area of Science:
- Pharmacology
- Drug Interactions
- Clinical Pharmacokinetics
Background:
- Dihydropyridine calcium channel blockers' oral bioavailability is often increased by grapefruit juice.
- Naringin in grapefruit juice is a known inhibitor of CYP3A4, a key enzyme in drug metabolism.
Purpose of the Study:
- To investigate the pharmacokinetic interaction between grapefruit juice and nimodipine.
- To determine the effect of grapefruit juice on nimodipine bioavailability and its metabolites.
Main Methods:
- A randomized crossover study involving eight healthy young men.
- Nimodipine was administered with water or grapefruit juice, with plasma concentrations measured up to 24 hours.
- Pharmacokinetic parameters were estimated using model-independent analysis.
Main Results:
- Grapefruit juice increased nimodipine's area under the curve (AUC) by 51% and Cmax by 24%.
- The 90% confidence intervals for AUC (114%-200%) and Cmax (0.76-2.01) indicated a significant interaction.
- Metabolite AUC to parent drug AUC ratios were reduced, suggesting altered metabolism.
Conclusions:
- Grapefruit juice significantly alters nimodipine pharmacokinetics, increasing its exposure.
- A relevant interaction between grapefruit juice and nimodipine was confirmed.
- Nimodipine should not be co-administered with grapefruit juice due to increased bioavailability and potential for enhanced effects.
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