Effects of Ingestion of Grapefruit Juice or Grapefruit on the Hypotensive Effect and Plasma Concentrations of Dihydropyridine Calcium Antagonists (Amlodipine and Nifedipine): A Case Study

Abstract

The purpose of this study was to examine the effects of ingestion of grapefruit juice or grapefruit on the hypotensive effect and plasma concentration of dihydropyridine calcium antagonists, i.e., amlodipine and nifedipine. A 50-year-old man with essential hypertension was studied. Grapefruit juice (500 ml) was taken together with the antihypertensive drug, while one grapefruit was taken before drug ingestion. Blood pressures were measured using a digital automatic blood pressure monitor over a certain period. A single ingestion of grapefruit juice had no effect on plasma amlodipine concentration, but rapidly increased plasma nifedipine concentration and decreased blood pressure, while the effect on blood pressure was short-lasting. Grapefruit had no effect on either drug. It should be of concern that ingestion of a relatively large volume of grapefruit juice causes rapid decrease in blood pressure when the subject is treated by nifedipine.

Keywords:

• blood pressure
• grapefruit juice
• grapefruit
• calcium antagonist
• amlodipine
• nifedipine