Co‐administration of ketoconazole with H1‐antagonists ebastine and loratadine in healthy subjects: pharmacokinetic and pharmacodynamic effects
Open Access
- 20 January 2005
- journal article
- clinical trial
- Published by Wiley in British Journal of Clinical Pharmacology
- Vol. 59 (3), 346-354
- https://doi.org/10.1111/j.1365-2125.2005.02348.x
Abstract
Aims Two studies were conducted to evaluate the effects of coadministration of ketoconazole with two nonsedating antihistamines, ebastine and loratadine, on the QTc interval and on the pharmacokinetics of the antihistamines. Methods In both studies healthy male subjects (55 in one study and 62 in the other) were assigned to receive 5 days of antihistamine (ebastine 20 mg qd in one study, and loratadine 10 mg qd in the other) or placebo alone using a predetermined randomization schedule, followed by 8 days of concomitant ketoconazole 450 mg qd/antihistamine or ketoconazole 400 mg qd/placebo. Serial ECGs and blood sampling for drug analysis were performed at baseline and on study days 5 (at the end of monotherapy) and 13 (at the end of combination therapy). QT intervals were corrected for heart rate using the formula QTc = QT/RRα with special emphasis on individualized α values derived from each subject's own QT/RR relationship at baseline. Results No significant changes in QTc interval from baseline were observed after 5 days administration of ebastine, loratadine or placebo. Ketoconazole/placebo increased the mean QTc (95% CI) by 6.96 (3.31–10.62) ms in the ebastine study and by 7.52 (4.15–10.89) ms in the loratadine study. Mean QTc was statistically significantly increased during both ebastine/ketoconazole administration (12.21 ms; 7.39–17.03 ms) and loratadine/ketoconazole administration (10.68 ms; 6.15–15.21 ms) but these changes were not statistically significantly different from the increases seen with placebo/ketoconazole (6.96 ms; 3.31–10.62 ms), P = 0.08 ebastine study, (7.52 ms; 4.15–10.89 ms), P = 0.26 loratadine study). After the addition of ketoconazole, the mean area under the plasma concentration–time curve (AUC) for ebastine increased by 42.5 fold, and that of its metabolite carebastine by 1.4 fold. The mean AUC for loratadine increased by 4.5 fold and that of its metabolite desloratadine by 1.9 fold following administration of ketoconazole. No subjects were withdrawn because of ECG changes or drug‐related adverse events. Conclusions Ketoconazole altered the pharmacokinetic profiles of both ebastine and loratadine although the effect was greater for the former drug. The coadministration of ebastine with ketoconazole resulted in a non significant mean increase of 5.25 ms (−0.65 to 11.15 ms) over ketoconazole with placebo (6.96 ms) while ketoconazole plus loratadine resulted in a nonsignificant mean increase of 3.16 ms (−2.73 to 8.68 ms) over ketoconazole plus placebo (7.52 ms). Changes in uncorrected QT intervals for both antihistamines were not statistically different from those observed with ketoconazole alone. The greater effect of ketoconazole on the pharmacokinetics of ebastine was not accompanied by a correspondingly greater pharmacodynamic effect on cardiac repolarization.Keywords
This publication has 26 references indexed in Scilit:
- Effects of supratherapeutic doses of ebastine and terfenadine on the QT intervalBritish Journal of Clinical Pharmacology, 2002
- Evaluation of Drug-Induced QT Interval ProlongationDrug Safety, 2001
- Evaluation of the pharmacokinetics and electrocardiographic pharmacodynamics of loratadine with concomitant administration of ketoconazole or cimetidineBritish Journal of Clinical Pharmacology, 2000
- Cardiac Actions of AntihistaminesAnnual Review of Pharmacology and Toxicology, 1996
- Cardiac Actions of AntihistaminesAnnual Review of Pharmacology and Toxicology, 1996
- Identification of Human Liver Cytochrome P450s Involved in the Microsomal Metabolism of the Antihistaminic Drug LoratadineInternational Archives of Allergy and Immunology, 1995
- Terfenadine-ketoconazole interaction. Pharmacokinetic and electrocardiographic consequencesJama-Journal Of The American Medical Association, 1993
- Exponential correction of QT interval to minimize the effect of the heart rate in children.Japanese Circulation Journal, 1993
- The normal Q-T intervalAmerican Heart Journal, 1962
- Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei HerzkrankenActa Medica Scandinavica, 1920