Zithrocin Drug Interactions

Azithromycin may interact with antacids containing aluminum or magnesium salts and should be given at least an hour before or 2 hours after the antacid. Erythromycin and other macrolides have the potential to interact with a large number of drugs through their action on the hepatic cytochrome P450 isoenzymes, particular CYP1A2 and CYP3A4. These interactions can result in severe adverse effects, including ventricular arrhythmias with astemizole, cisapride and tertenadine. Other macrolides including azithromycin and dirithromycin are reported to have little or no effect on hepatic cytochrome, and consequently may produce fewer drug interactions.
Other mechanisms by which macrolides cause interactions include suppression of the gastrointestinal flora responsible for the inhaluminal metabolism of digoxin and possibly oral contraceptives, and the stimulant effect of macrolides on gastrointestinal motility which is believed to be responsible for the interaction between spiramycin and levodapa.
Serum concentrations of azithromycin are markedly increased when it is administered with nelfinavir, but the clinical significance of this is uncertain. Although dosage adjustment is not required the patient should be close monitored for adverse effects.
Macrolides have been reported rare to prolong the QT interval and should be used with caution with other drugs known to also have this effect.
Azithromycin may also interact with zidovudine, ergot derivates, coumarin and ciclosporin. Caution should be exercised before considering administration with these drugs.