Ketoconazole very markedly raised ebastine levels and markedly raised
loratadine levels. In one study, this was associated with a small increase in the QT interval for both
antihistamines, but there was no obvious alteration in the
adverse event profile. Ketoconazole markedly raised the
plasma levels of
fexofenadine, and modestly raised those of
desloratadine and emedastine, but these changes had no effect on the QT interval, or on adverse events. The combinations may therefore be assumed to be safe in terms of cardiac effects.
The manufacturer of ebastine advises against the use of
itraconazole or
ketoconazole. However, in general these changes are not expected to have a clinically relevant effect, although some caution may be warranted. Azelastine,
cetirizine, levocabastine and levocetirizine do not appear to interact with
ketoconazole and may therefore be suitable alternatives.