['Our objective was to evaluate the effects of itraconazole and grapefruit juice on the pharmacokinetics of the beta-adrenergic receptor-blocking agent celiprolol in healthy volunteers.', 'In a randomized 3-phase crossover study, 12 healthy volunteers took itraconazole 200 mg orally or placebo twice a day or 200 mL grapefruit juice 3 times a day for 2 days. On the morning of day 3, 1 hour after ingestion of itraconazole, placebo, or grapefruit juice, each subject ingested 100 mg celiprolol with 200 mL of water (placebo and itraconazole phases) or grapefruit juice. In addition, 200 mL of water or grapefruit juice was ingested 4 and 10 hours after celiprolol intake. The plasma concentrations of celiprolol, itraconazole, and hydroxyitraconazole and the excretion of celiprolol into urine were measured up to 33 hours after dosing. Systolic and diastolic blood pressures and heart rate were recorded with subjects in a sitting position before the administration of celiprolol and 2, 4, 6, and 10 hours later.', 'During the itraconazole phase, the mean area under the plasma concentration-time curve from 0 to 33 hours [AUC(0-33)] of celiprolol was 80% greater (P <.05) than in the placebo phase. During the grapefruit juice phase, the mean AUC(0-33) and peak plasma concentration values of celiprolol were reduced to about 13% (P <.001) and 5% (P <.001) of the respective placebo phase values. The cumulative excretion into urine of celiprolol was increased by 59% by itraconazole (P <.05) and decreased by 85% by grapefruit juice (P <.001). Hemodynamic variables did not differ between the phases.'] Does itraconazole increases but grapefruit juice greatly decrease plasma concentrations of celiprolol?