Comparative effects of nonsedating histamine H1 receptor antagonists, ebastine and terfenadine, on human Kv1.5 channels.

The effects of ebastine and terfenadine, long-acting nonsedating histamine H1 receptor antagonists, were studied on hKv1.5 channels using the whole-cell voltage-clamp configuration of the patch-clamp technique in Ltk- cells transfected with the gene encoding the hKv1.5 channel. Upon depolarization to +60 mV, terfenadine, 1 microM and 3 microM, inhibited the hKv1.5 current by 42.4 +/- 6.4% and 69.3 +/- 4.2% (P < 0.01). In contrast, at the same range of concentrations, ebastine-induced inhibition of this K+ current averaged 6.5 +/- 2.0% and 13.0 +/- 2.0 (P < 0.05). At the highest concentration tested (3 microM) neither terfenadine carboxylate nor carebastine significantly modified hKv1.5 current. All these results suggest that ebastine could represent a safer alternative to terfenadine in the clinical practice.