Effects of supratherapeutic doses of ebastine and terfenadine on the QT interval

Aims The objective of this study was to compare the effects of high doses of ebastine with terfenadine and placebo on QTc. Methods Thirty-two subjects were randomly assigned to four treatments (ebastine 60 mg day(-1), ebastine 100 mg day(-1), terfenadine 360 mg day(-1), placebo) administered for 7 days. Serial ECGs were performed at baseline and day 7 of each period. QT interval was analysed using both Bazett (QTcB) and Fridericia (QTcF) corrections. Results Ebastine 60 mg (+ 3.7 ms) did not cause a statistically significant change in QTcB compared with placebo (+ 1.4 ms). The mean QTcB for ebastine 100 mg was increased by + 10.3 ms which was significantly greater than placebo but was significantly less (P < 0.05) than with terfenadine 360 mg (+ 18.0 ms). There were no statistically significant differences in QTcF between ebastine 60 mg (-3.2 ms) or ebastine 100 mg (1.5 ms) and placebo (-2.1 ms); although terfenadine caused a 14.1 ms increase which was significantly different from the other three treatments. The increase in QTcB with ebastine most likely resulted from overcorrection of the small drug-induced increase in heart rate. Conclusions Ebastine at doses up to five times the recommended therapeutic dose did not cause clinically relevant changes in QTc interval.