Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.

Seek emergency medical attention if you think you have used too much of this medicine. Overdose symptoms may include nausea, vomiting, diarrhea, and stomach discomfort.

Do not take antacids that contain aluminum or magnesium within 2 hours before or after you take Zithromax. This includes Rolaids, Maalox, Mylanta, Milk of Magnesia, Pepcid Complete, and others. These antacids can make Zithromax less effective when taken at the same time.

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.

Avoid exposure to sunlight or artificial UV rays (sunlamps or tanning beds). Zithromax can make your skin more sensitive to sunlight and sunburn may result. Use a sunscreen (minimum SPF 15) and wear protective clothing if you must be out in the sun.