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Grapefruit juice ingestion significantly reduces talinolol bioavailability
Ute I Schwarz1, Diana Seemann, Reinhard Oertel
1Institute of Clinical Pharmacology, Medical Faculty, Technical University, and Medical Department I, Technical University Hospital, Dresden. ute.i.schwarz@vanderbilt.edu
Clinical Pharmacology and Therapeutics
|May 21, 2005
Summary
Grapefruit juice significantly reduced talinolol levels in the body, suggesting it inhibits intestinal uptake transporters, not P-glycoprotein. This effect was observed with both single and repeated consumption.
Area of Science:
- Pharmacology
- Drug Metabolism
- Gastrointestinal Physiology
Background:
- Grapefruit juice is known to affect drug pharmacokinetics.
- P-glycoprotein and intestinal uptake transporters play crucial roles in drug absorption.
Purpose of the Study:
- To investigate the impact of single and repeated grapefruit juice intake on talinolol pharmacokinetics.
- To determine if grapefruit juice affects P-glycoprotein or intestinal uptake transporters.
Main Methods:
- 24 healthy volunteers received 50 mg talinolol with water, single-strength grapefruit juice, or after 6 days of repeated grapefruit juice intake.
- Duodenal biopsy samples were analyzed for MDR1 mRNA and P-glycoprotein levels.
- Common MDR1 gene polymorphisms were assessed.
Main Results:
- Both single and repeated grapefruit juice intake significantly decreased talinolol's area under the curve (AUC) and peak concentration (Cmax).
- Grapefruit juice did not alter talinolol's renal clearance, elimination half-life, or time to Cmax.
- MDR1 mRNA, P-glycoprotein levels, and MDR1 genotypes were unaffected by grapefruit juice.
Conclusions:
- Grapefruit juice constituents appear to inhibit intestinal uptake transporters, not P-glycoprotein, affecting talinolol pharmacokinetics.
- Grapefruit juice does not alter intestinal P-glycoprotein expression.