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Zithromax: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Dec 30, 2022.

1. How it works

  • Zithromax is a brand (trade) name for azithromycin.
  • Zithromax (azithromycin) works by preventing bacteria from making certain types of protein and may be used to treat infections caused by susceptible bacteria such as Mycobacterium avium, M. intracellulare, and Chlamydia trachomatis.
  • Zithromax belongs to the class of medicines known as macrolide antibiotics.

2. Upsides

  • Used to treat infections caused due to susceptible bacteria that occur on the skin, in the lungs, and in the ears.
  • Also treats some sexually transmitted infections; however, should not be relied upon to treat gonorrhea or syphilis.
  • Used specifically for the treatment and prevention of mycobacterium avium complex (a type of respiratory infection) in people with advanced HIV. May be used in addition to other antibiotics.
  • Active against a wide range of microorganisms and shows good penetration into human tissue. Some bacteria may be resistant (not killed by Zithromax).
  • May be better tolerated and have more effective tissue penetration than other similar antibiotics such as erythromycin.
  • Can be dosed once daily which improves adherence.
  • May be used to treat bacterial infections in people intolerant of penicillins.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Nausea, diarrhea, vomiting, abdominal pain, dyspepsia, flatulence, fatigue, and headache.
  • May cause liver damage which can affect liver function, sometimes fatally. Zithromax must be discontinued if any signs of liver dysfunction occur.
  • May cause changes in the way the heart beats, resulting in the development of cardiac arrhythmias. The risk is greater in people with a history of QT prolongation, on other drugs known to prolong the QT interval, with low levels of potassium or magnesium in their blood, and in those receiving anti-arrhythmic agents such as sotalol, amiodarone, and procainamide.
  • Clostridium difficile-associated diarrhea is a potential side effect of almost all antibacterial agents, including Zithromax. Zithromax should be discontinued if this develops; symptoms include severe diarrhea.
  • May cause severe skin reactions and photosensitivity (increased sensitivity to sunlight). Discontinue Zithromax and seek urgent medical advice should a rash develop.
  • May interact with some other medications including warfarin and nelfinavir.
  • The dosage of Zithromax may need to be decreased in those with renal disease and Zithromax may not be suitable for people with myasthenia gravis. Use in neonates has been associated with infantile hypertrophic pyloric stenosis (IHPS). Symptoms may include vomiting and irritability. May not be effective as the sole therapy for treating gonorrhea or syphilis.
  • Has not been associated with an increased risk of birth defects when used to treat bacterial infections in pregnant women. Weigh up the risks versus benefits before administering to pregnant women. Zithromax has been detected in human milk and the infant should be monitored for diarrhea, vomiting, or a rash if it is decided to continue with breastfeeding while being administered Zithromax.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Zithromax is an antibiotic used to treat a variety of different infections and it appears to have better tissue penetration and tolerability than similar antibiotics, such as erythromycin. Zithromax has the distinct advantage of once-daily dosing; however, diarrhea is a common side effect.

5. Tips

  • May be taken with or without food; however, Zithromax tablets may be better tolerated if taken with food.
  • Do not take at the same time as aluminum or magnesium-containing antacids.
  • Discontinue Zithromax immediately and seek urgent medical advice if any signs of an allergic reaction (such as a rash or difficulty breathing) occur.
  • Take exactly as directed and finish the course as prescribed by your doctor, even if you feel better. Skipping doses or not completing treatment can decrease the effectiveness of the treatment and promote the development of resistance.
  • Although diarrhea is common with Zithromax, contact your doctor if you develop severe diarrhea especially if it is very watery or contains blood. Sometimes diarrhea may occur one to two months after starting or finishing a course of Zithromax.
  • Contact your doctor immediately if you develop any signs of liver disease such as yellowing of the skin or whites of the eyes, upper right abdominal pain, rash, clay-colored stools, severe nausea, and vomiting.
  • If you are allergic to other macrolides (such as clarithromycin, erythromycin, or telithromycin) do not take Zithromax. Also, avoid Zithromax if you have taken it before and it caused damage to your liver.
  • Take Zithromax oral suspension immediately after reconstituting (mixing up). Do not store for later use.
  • Avoid excessive exposure to sunlight or tanning beds. Use an SPF 30 or higher sunblock when outside and wear protective clothing because Zithromax can make you burn more easily in the sun.
  • Tell your doctor if you are pregnant or breastfeeding before taking Zithromax.

6. Response and effectiveness

  • Takes between two and a half to just over three hours for peak concentrations to be reached. A loading dose (a higher-than-normal starting dose) may be used to reach steady concentrations sooner.
  • Can be dosed once daily.
  • May take several days before symptoms of the infection start to abate. Always finish the course as prescribed.

7. Interactions

Medicines that interact with Zithromax may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Zithromax. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Zithromax include:

  • amiodarone
  • apixaban
  • aspirin
  • BCG live (Theracrys)
  • dabigatran
  • dalteparin
  • digoxin
  • dronedarone
  • live typhoid vaccine
  • mifepristone
  • NSAIDs, such as ibuprofen, diclofenac, and naproxen
  • pimozide
  • quinidine

In general, any medicine that can increase the risk of bleeding (such as clopidogrel, SSRI antidepressants, and fish oils) may interact with Zithromax. Alcohol may increase the side effects of Zithromax and there is the potential for grapefruit products to interact with Zithromax; however, reports are uncommon.

Note that this list is not all-inclusive and includes only common medications that may interact with Zithromax, You should refer to the prescribing information for Zithromax for a complete list of interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Zithromax only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: December 30, 2022.