Zithromax - Use | Dose | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Zithromax (azithromycin) is an antibacterial drug intended for systemic use. It belongs to a group of medicines called macrolide antibiotics. Chemically, Zithromax is classified as azalide antibiotic. It was created when the nitrogen atoms are added in the lactone ring of erythromycin molecule (another antibiotic).

Mechanism of action

The mechanism of action of this drug is based on the suppression of protein synthesis of bacteria that occurs as a result of the drug binding to the 50S ribosomal subunit and inhibition of peptide translocation.

Resistance to this medicine may occur and it can be acquired or natural. Three basic mechanisms of bacterial resistance to this drug include:

  • Changes of the target site
  • Changes in transport antibiotics
  • Modification of antibiotics


Zithromax is used in the following indications:

  • Bronchitis
  • Sinusitis
  • Outpatient pneumonia
  • Pharyngitis
  • Tonsillitis
  • Otitis media
  • Skin infections
  • Soft tissue infections
  • Uncomplicated genital infections caused by Chlamydia

Contraindications and precautions

Zithromax is contraindicated in the following conditions:

  • Allergy to azithromycin, or any other macrolide antibiotic

Caution should be exercised in the following situations:

  • In patients with significant hepatic impairment. There are reports of hepatotoxicity in patients taking this drug.1
  • In patients who are taking ergot alkaloids (drugs used to treat migraines). Co-administration of these drugs with Zithromax, increases the risk of ergotism (ergot alkaloids poisoning).
  • In patients who have arrhythmias or other cardiac diseases. Zithromax is associated with torsade de pointes - dangerous type of arrhythmias.2
  • In patients with myasthenia gravis. There are reported cases of myasthenia gravis exacerbations in patients taking this medicine.

Zithromax, pregnancy and lactation

In one study where 129 pregnant women participated, there were no recorded malformations caused by this drug.3 Therefore, this drug is classified in the group B, but it can be applied only with the recommendation and supervision of a physician.

It passes into breast milk, so breastfeeding should be avoided while you're taking this drug.


Two dosing regimen may be applied:

  • The first dosing regimen: On the first day of treatment, you should take 250 mg of Zithromax in the morning and the evening, then 250 mg once a day for the next four days.
  • The second dosing regimen: Take 500 mg once a day for three days.

The tablets are intended only for patients whose body weight exceeds 100 pounds (45 kg).

Your doctor will determine the method of administration of the drug for you.


Zithromax can interact with the following medications:

  • Cyclosporine
  • Ergot alkaloids
  • Warfarin
  • Theophylline
  • Digoxin
  • Anti-arrhythmics (e.g. amiodarone)
  • Efavirenz and nelfinavir
  • Cisapride
  • Antacids
  • Triazolam
  • Fentanyl and methadone
  • Antipsychotics (e.g. clozapine and haloperidol)

Side effects

Zithromax may cause the following side effects:

  • Pain in the ear
  • Fever
  • Loss of appetite
  • Hiccups
  • Feeling of tightness in the chest
  • Vision problems
  • Hearing problems
  • Mood swings and depression
  • Flu-like symptoms
  • Allergy


  1. NCBI link 1
  2. NCBI link 2
  3. NCBI link 3

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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