Ketoconazole (and therefore probably itraconazole) can cause moderate increases in the
serum levels of
sibutramine and its two metabolites. Small increases in heart rates have also been reported seen although there were no associated ECG changes.
The manufacturers caution concurrent use with both
ketoconazole and itracona- zole. Note that
sibutramine alone can cause an increase in heart rate, and a rate increase of 10 bpm is an indication to stop the drug.