Azithromycin: what it treats and how to use it safely

Azithromycin is a common antibiotic you’ll see prescribed for respiratory infections, some skin infections, certain sexually transmitted infections, and ear infections. It belongs to the macrolide family and works by stopping bacteria from making proteins they need to grow. That makes it useless against viruses like the flu or common cold, so don’t expect it to help with viral illnesses.

One big advantage is convenience: many azithromycin regimens are short and simple. The classic “Z‑Pak” is 500 mg on day one then 250 mg daily for four more days. For some infections doctors use 500 mg once daily for three days. Pediatric doses are based on weight—your doctor or pharmacist will give exact instructions. Always follow the prescribed schedule and finish the course unless your clinician tells you otherwise.

Common side effects and when to call your doctor

Most people tolerate azithromycin well. The most common side effects are nausea, diarrhea, stomach pain, and mild headaches. Less common but more serious reactions include severe allergic reactions, jaundice or signs of liver damage, and hearing changes. Azithromycin can also affect heart rhythm by prolonging the QT interval. If you get fast/irregular heartbeat, fainting, or severe dizziness, stop the drug and seek urgent care.

Tell your clinician right away if you have a known heart rhythm problem, low potassium or magnesium, or if you take other drugs that affect the heart’s rhythm. Also report any signs of a severe skin reaction or unexpected bruising or bleeding.

Key drug interactions and precautions

Azithromycin has fewer drug interactions than some other macrolides, but some still matter. Combining it with other QT‑prolonging drugs (certain antipsychotics, some antidepressants, fluoroquinolones) increases the risk of dangerous heart rhythm changes. Antacids containing aluminum or magnesium can reduce azithromycin absorption, so take the antibiotic at least 1 hour before or 2 hours after those antacids. If you’re on warfarin, some patients need closer INR monitoring while taking azithromycin.

Adjustments may be needed for severe liver disease. Azithromycin is often used in pregnancy when needed, but always confirm with your provider. If you’re breastfeeding, discuss risks and benefits—small amounts pass into breast milk.

Resistance is a real problem. Don’t pressure clinicians for azithromycin when an infection is likely viral. Overuse drives resistance in common bacteria like Streptococcus and some sexually transmitted pathogens. If symptoms don’t improve within 48–72 hours or get worse, contact your clinician for reassessment—sometimes a different antibiotic or further testing is needed.

Storage is simple: keep tablets at room temperature away from moisture. If you miss a dose, take it as soon as you remember unless it’s almost time for the next dose—don’t double up. If you have questions about dosing, interactions, or side effects, talk to your pharmacist or doctor. Using azithromycin correctly keeps it effective for you and for others down the road.