Geriatrics
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Concomitant administration of grapefruit juice can increase the plasma concentration of numerous drugs in humans and decrease the concentration of a few others. Such elevations of drug plasma concentrations have, on occasion, resulted in adverse clinical effects. ⋯ The effect of grapefruit juice on drug metabolism is most pronounced in drugs with a high first-pass metabolism (eg, felodipine, amiodarone), in which it inhibits the first-pass metabolism of the CYP 3A4 substrates leading to an increase in Cmax and area under the concentration time curve (AUC). The use of grapefruit juice with a few specific drugs (eg, fexofenadine, digoxin) may lower plasma drug concentrations by inhibiting drug absorption catalyzed by the organic anion transporting polypeptide (OATP).