Azithromycin – Uses


Azithromycin is a broad-spectrum macrolide antibiotic with a long half-life and a high degree of tissue penetration 3. It was initially approved by the FDA in 1991.

It is primarily used for the treatment of respiratory, enteric and genitourinary infections and may be used instead of other macrolides for some sexually transmitted and enteric infections. It is structurally related to erythromycin.

Azithromycin [9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin] is a part of the azalide subclass of macrolides, and contains a 15-membered ring, with a methyl-substituted nitrogen instead of a carbonyl group at the 9a position on the aglycone ring, which allows for the prevention of its metabolism. This differentiates azithromycin from other types of macrolides.

azithromycin tablet.png

Brand Names

Azasite, Zithromax, Zmax


Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Identity of Azithromycin

Type of medicine Antibiotics
Synonyms Azithromycin, Azithromycine, Azithromycinum, Azitromicina
Molecular Formula C38H72N2O12
Molecular Weight 748.9845 g/mol
IUPAC Names (2R,3S,4R,5R,8R,10R,11R,12S,13S,14R)-11-[(2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyloxan-2-yl]oxy-2-ethyl-3,4,10-trihydroxy-13-[(2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyloxan-2-yl]oxy-3,5,6,8,10,12,14-heptamethyl-1-oxa-6-azacyclopentadecan-15-one
Structural formula of main components Azithromycin_structure.png
Pure active ingredient Azithromycin
Appearance White film-coated oval shaped biconvex tablets
Melting point 129-135°C
Available as Tablets, capsules, and liquid
Prescription Azithromycin is available on prescription

Why is this medication prescribed?

Azithromycin is used to treat certain bacterial infections, such as bronchitis; pneumonia; sexually transmitted diseases (STD); and infections of the ears, lungs, sinuses, skin, throat, and reproductive organs. Azithromycin also is used to treat or prevent disseminated Mycobacterium avium complex (MAC) infection [a type of lung infection that often affects people with human immunodeficiency virus (HIV)]. Azithromycin is in a class of medications called macrolide antibiotics. It works by stopping the growth of bacteria.

Antibiotics such as azithromycin will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resist antibiotic treatment.

Azithromycin side effects

Azithromycin oral tablet doesn’t cause drowsiness, but it can cause other side effects.

More common side effects

The more common side effects of azithromycin oral tablet can include:

  • Diarrhea
  • Nausea
  • Abdominal (belly) pain
  • Vomiting
  • Headache

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life threatening or if you think you’re having a medical emergency. Serious side effects can include:

  • Liver problems. Symptoms can include:
    • Tiredness or weakness
    • Loss of appetite
    • Pain in your upper abdomen (belly)
    • Dark urine
    • Yellowing of your skin or the whites of your eyes
  • QT prolongation, which can cause a fast or irregular heart rhythm. Symptoms can include:
    • Feeling fluttering in your chest
    • Gasping while sleeping
    • Fainting
  • Allergic reactions. Symptoms can include:
    • Trouble breathing
    • Swelling of your face, lips, tongue, or throat
    • Hives
    • Severe skin reactions, such as Stevens-Johnson syndrome, acute generalized exanthematous pustulosis (AGEP), or toxic epidermal necrolysis, which can cause symptoms such as red, blistering skin or skin sloughing (shedding dead skin cells)
  • Diarrhea that’s caused by bacteria called Clostridium difficile (C. diff). In addition to diarrhea, symptoms can include:
    • Fever
    • Abdominal (belly) pain
    • Nausea
    • Reduced appetite
  • Infantile hypertrophic pyloric stenosis (narrowing or blocking in part of the digestive system in newborns). Symptoms can include:
    • Vomiting after eating
    • Irritability with feeding
    • Lack of weight gain

If you have an allergic reaction, call your doctor or local poison control center right away. Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could cause death.

Mechanism of action

In order to replicate, bacteria require a specific process of protein synthesis, enabled by ribosomal proteins. Azithromycin binds to the 23S rRNA of the bacterial 50S ribosomal subunit. It stops bacterial protein synthesis by inhibiting the transpeptidation/translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit. This results in the control of various bacterial infections. The strong affinity of macrolides, including azithromycin, for bacterial ribosomes, is consistent with their broad‐spectrum antibacterial activities.

Azithromycin is highly stable at a low pH, giving it a longer serum half-life and increasing its concentrations in tissues compared to erythromycin

Drug interactions

Azithromycin may interact with other medications a person is taking.

For example, using azithromycin while taking nelfinavir, which is a drug that helps treat HIV, can increase the risk of liver abnormalities and hearing problems.

Azithromycin can also increase the effects of blood thinners such as warfarin.

Other drugs that may interact with azithromycin include:

  • Digoxin, a heart medication
  • Colchicine, a gout medication
  • Phenytoin, a seizure medication
  • Antacids that contain magnesium or aluminum

A person should tell a doctor about all current medications, supplements, and remedies before taking azithromycin. Always speak to a doctor before stopping taking medications.

How to take it?

Azithromycin is a prescription medication. Therefore, people should not take it without a prescription.

The drug is available in the form of a tablet, an oral suspension solution, an eye drop, and an injection. The best type and dosage depend on the infection a person has.

People can take the drug with or without food. They should thoroughly shake the liquid form before use.

Some examples of common dosages include:

Infection Dosage
Community-acquired pneumonia
Skin infections
An initial dose of 500 milligrams (mg) followed by 250 mg once daily until day 5
Mild-to-moderate bacterial COPD exacerbations 500 mg per day for 3 days OR an initial dose of 500 mg followed by 250 mg once daily until day 5
Sinus infections 500 mg per day for 3 days
Chancroid genital ulcers A single dose of 1 gram (g)
A single dose of 1 g
Gonococcal urethritis
A single dose of 2 g

Using antibiotics incorrectly can lead to the development of drug-resistant strains of bacteria, meaning that antibiotics no longer work against them. This is called antibiotic resistance.

In case of overdose

If you take too much azithromycin, you could have dangerous levels of the drug in your body. This may cause liver damage and irregular heart rhythm. If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest emergency room right away.


You should not use azithromycin if you have ever had jaundice or liver problems when you have previously taken this medicine.

Before taking this medicine

You should not use azithromycin if you are allergic to it, or if:

  • You have ever had jaundice or liver problems caused by taking azithromycin; or
  • You are allergic to similar drugs such as clarithromycin, erythromycin, or telithromycin.

To make sure azithromycin is safe for you, tell your doctor if you have ever had:

  • Liver disease;
  • Kidney disease;
  • Myasthenia gravis;
  • A heart rhythm disorder;
  • Low levels of potassium in your blood; or
  • Long QT syndrome (in you or a family member).

This medicine is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It is not known whether azithromycin passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Pregnancy, breastfeeding and fertility while taking azithromycin

Azithromycin and pregnancy

Azithromycin is generally thought to be OK to take during pregnancy if you have an infection that needs treatment. However, other antibiotics may be more suitable for you, depending on your type of infection.

Talk to your doctor about taking azithromycin as it should only be taken if the benefits outweigh the possible risks.

Azithromycin and breastfeeding

If your doctor or health visitor says that your baby is healthy, it’s OK to take azithromycin while breastfeeding.

Azithromycin passes into breast milk in small amounts. It has not been known to cause any side effects in breastfed babies.

Talk to your health visitor, midwife, pharmacist, or doctor as soon as possible if:

  • your baby is not feeding as well as usual or has an upset stomach
  • your baby has a rash or oral thrush (a fungal infection in their mouth)
  • you have any other concerns about your baby

Azithromycin and fertility

There’s no clear evidence to suggest that taking azithromycin reduces fertility in either men or women.

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