Zithromax (azithromycin) is prescribed for patients diagnosed with some infections caused by the presence of bacteria in the body. Zithromax is efficient against bacteria-induced infections only and will not treat cold and flu. In case of being allergic to this medicines, as well as clarithromycin, dirithromycin, or erythromycin you will need to talk to your health care provider about an alternative, as taking Zithromax may not be safe for you. A severe allergic reaction may develop if you take Zithromax in spite of the history of an allergic reaction. The following symptoms may indicate a severe allergic reaction: hives, rash, trouble breathing and swallowing, itching and swelling. You need to seek emergency medical help if you get these symptoms. If there are any medical conditions you have or used to have – notify your doctor of them. Make sure to mention the following ones: cystic fibrosis, human immunodeficiency virus, kidney or liver disease, and irregular heartbeat, as well as any other ones you think may be of importance. Your doctor also needs to know as much as possible about the drugs you are currently taking or intended to take. There are a number of medications that have been reported to cause interactions when combined with Zithromax. Therefore, they need to be avoided throughout the entire period of the treatment (usually from 1 to 5 days). The following drugs are supposed to be reported: calcium channel blockers, theophylline, cholesterol-lowering medicines, phenytoin, carbamazepine, ergot medicines, other antibiotics, pimozide, digoxin, HIV medicines, triazolam, and warfarin. If you go to some other doctor and are about to be prescribed some other medicine – make sure you mention the fact of using Zithromax at the moment. Serious side effects of Zithromax are quite rare but you still need to be aware of their possibility. The following serious side effects are possible: uneven heartbeats, headache with a severe blistering, red skin rash, stomach pain, clay-colored stools, loss of appetite, dark urine, watery or bloody diarrhea, low fever, and chest pain. Less serious side effects, however, are more likely to occur. The following are considered to be mild side effects that are not supposed to be reported to your health care provider: skin rash, stomach upset, stomach pain, mild nausea, mild itching, diarrhea, nervous feeling, dizziness, ringing in your ears, constipation, insomnia, vomiting, headache, and decreased sense of taste. You will need to take this medication for as long as prescribed by your health care provider. Avoid taking more of Zithromax than prescribed, as this is not likely to increase the efficiency of your treatment. An overdose of Zithromax can cause the following symptoms that you will need to report to your local emergency center: stomach discomfort, diarrhea, nausea, and vomiting. This drug is FDA pregnancy category B. Zithromax is not expected to be harmful to an unborn baby but you still need to report the fact of being pregnant or breastfeeding to your health care provider.