Zithromax (azithromycin) has been specially designed for the needs of people with bacterial infections whose immune system is unable to fight off the disease without additional help. Sometimes Zithromax is used to prevent heart infections and STD in victims of sexual assault. Tell your health care provider if you are allergic to other macrolide antibiotics, or actually azithromycin, as this may result in a number of very unpleasant health effects if you start taking Zithromax anyway. Tell your doctor if you have liver disease, cystic fibrosis, HIV, irregular heartbeat, or kidney disease, as you may need a dose adjustment before you even start taking Zithromax. Tell your doctor about any medications you are using - especially digoxin, pimozide, ergot medicines, another antibiotic, triazolam, HIV medicines, theophylline, cyclosporine, warfarin, calcium channel blockers, cholesterol-lowering medicines, carbamazepine, or phenytoin. If you get such mild side effects as diarrhea, ringing in your ears, constipation, insomnia, mild itching or skin rash, vomiting, stomach pain, dizziness, headache, or mild nausea, - there is no need to worry, as they are most likely to go away on their own.