You should not use azithromycin if you are allergic to it, or if: you have ever had jaundice or liver problems caused by taking azithromycin; or you are allergic to similar drugs such as clarithromycin, erythromycin, or telithromycin. To make sure azithromycin is safe for you, tell your doctor if you have: liver disease; kidney disease; myasthenia gravis; a heart rhythm disorder; or a history of Long QT syndrome. This medicine is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant. It is not known whether azithromycin passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby. Do not give this medicine to a child younger than 6 months old.