Lack of effect of erythromycin and ketoconazole on the pharmacokinetics and pharmacodynamics of steady-state intranasal levocabastine

The single-dose effects of the cytochrome P-450 inhibitors erythromycin and ketoconazole on the steady-state pharmacokinetics and electrocardiographic repolarization pharmacodynamics of intranasal levocabastine, a potent and selective H-1-receptor antagonist were evaluated in healthy young male subj ects. Two randomized, open-label, placebo-controlled; two-way crossover stu dies were performed Levocabastine nasal spray was administered as two spray s per nostril (0.05 mg/spray) twice daily (For a total daily dose of 0.4 mg )for 6 days. On Day 7, a single dose of 0.2 mg was administered followed im mediately by a single dose of either oral placebo, erythromycin 333 mg, or ketoconazole 200 mg. In all treatment groups, levocabastine was rapidly abs orbed, with peak plasma concentrations reached at approximately 3 hours in the erythromycin study and 2.8 hours in the ketoconazole study. The mean te rminal half-life was approximately 45 and 44 hours, respectively. In both s tudies, mean steady-state plasma concentrations and pharmacokinetics of lev ocabastine following the single doses of erythromycin or ketoconazole were not significantly different from corresponding values seen with the concomi tant administration of the placebo. No clinically significant mean changes from baseline in QT or QT(c) (QT corrected for heart rate) intervals occurr ed in any of the treatment groups, and none of the subjects in either study experienced abnormally prolonged QT(c) intervals. Intranasal levocabastine was well tolerated, with no difference in the incidence of adverse events between treatment groups in either study; adverse events were generally mil d in severity Since levocabastine undergoes only minimal hepatic metabolism and is not a substrate for or an inhibitor of cytochrome P-450, the likeli hood of systemic drug interactions with drugs affecting the cytochrome P-45 0 system is minimal. Journal of Clinical pharmacology, 1999;39:76-85 (C) 19 99 the American College of Clinical pharmacology.