Discontinue use if allergic reactions occur. Risk of hepatotoxicity, superinfection,
C. difficile-associated diarrhea, ergotism (w/ ergot derivatives). Renal impairment; myasthenia gravis. Prolonged cardiac repolarization & QT interval in patients w/ congenital or documented QT prolongation; currently receiving QT-prolonging drugs (eg, antiarrhythmics class IA & III, antipsychotics, antidepressants & fluoroquinolones); electrolyte disturbance particularly in cases of hypokalemia & hypomagnesemia; clinically relevant bradycardia, cardiac arrhythmia or insufficiency. Pregnancy & lactation. Elderly.