Potential side effects that can be caused by Zithromax apply to all dosage forms the drug is manufactured in: intravenous powder for solution, oral capsule, oral pill, oral powder for suspension, and oral powder for suspension (delayed release). Generally, all adverse reactions that may occur are subdivided into two major categories; within each category side effects caused by Zithromax are subsequently subdivided into more common, less common and rare:
1. Side effects that require immediate check with your physician are the following:
- More common: loose stools or diarrhea.
- Less common: fever or swelling, dry, cracked or scaly skin, crusting, itching, reddening or blistering of the skin.
- Rare: nausea or vomiting, abdominal or stomach pain, indigestion, black, tarry, or bloody stools, dark, cloudy or bloody urine, burning while urinating, chills or general feeling of illness or discomfort, cough, dizziness, drowsiness, fainting, fast, irregular or racing pulse or heartbeat, joint or muscle pain, noisy breathing, stuffy or runny nose, yellow eyes or skin, earache, and some others.
2. Rare side effects that may occur during the “body-adjusting-to-the-drug” period do not require medical attention. These can be the following: sour stomach, belching, change in taste or the color of the tongue, burning feeling in the stomach or chest, shortness of breath, numbness, prickling, itching, crawling or burning feelings, dysphoria or euphoria, nervousness, restlessness, shaking, sore mouth or tongue and some others.
It should be noted once again: it will be much easier for your physician to prevent any possible adverse reaction or tell you how to reduce the negative effect of that if you inform him/her about any single aspect and detail of your case history.
More information about side effects of Zithromax (Azithromycin): 
Zithromax 250mg caps | Azithromycin 250mg & 500mg