Som for macrolider, grundet potentiale for øgning af QT intervallet, bør Ketek anvendes med forsigtighed til patienter med coronare hjertesygdomme, ventrikulære arytmier ukorrigeret hypokaliæmi og/ eller hypomagnesiæmi, bradykardi (< 50 / min), eller under samtidig administration af Ketek med QT interval forlængende midler eller potente CYP3A4 inhibitorer såsom protease hæmmere og ketoconazol.
As with macrolides, due to a potential to increase QT interval, Ketek should be used with care in patients with coronary heart disease, a history of ventricular arrhythmias, uncorrected hypokalaemia and or hypomagnesaemia, bradycardia (< 50 bpm), or during concomitant administration of Ketek with QT interval prolonging agents or potent CYP 3A4 inhibitors such as protease inhibitors and ketoconazole.