Azithromycin is an antibiotic indicated for the treatment of bacterial infections such as sinusitis, pneumonia, skin infections, and sexually transmitted infections such as gonorrhea and chlamydia.

Azithromycin comes in 250, 500, and 600 mg pills and as an oral suspension containing 300, 600, 900, or 1200 mg per bottle (100 mg/5mL or 200 mg/5 mL after reconstitution). It is sold as the generic "azithromycin" as well as under the brand name Zithromax. Azithromycin is only available with a prescription.

Azithromycin can also be given in the hospital as an intravenous injection under the supervision of a doctor.

woman smiling and holding a pill in one hand and a cup of water in the other

Indications for use

Azithromycin is indicated for the treatment of certain bacterial infections, including:

Sinusitis;
Pharyngitis;
Bronchitis;
Pneumonia;
Acute otitis media;
Abscesses;
Furuncles (boils);
Infected skin ulcers;
Urethritis;
Cervicitis.

Azithromycin can also be used for the treatment of sexually transmitted infections, primarily chlamydia. It is effective against the bacteria Chlamydia trachomatis, Haemophilus ducreyi, and Neisseria gonorrhoeae, which cause chlamydia, chancroid, and gonorrhea, respectively.

Can azithromycin be used to treat COVID-19?

Azithromycin may be indicated for the treatment of COVID-19 complicated by bacterial pneumonia.

Azithromycin has no effect against viruses, including the coronavirus, and is only indicated for the treatment of associated bacterial infections.

Dosing instructions

Azithromycin comes in pill form and as an oral suspension and should be taken by mouth, before or after a meal, at the times indicated by your doctor or other prescribing provider.

1. Azithromycin pills

Dosing will depend on the type of infection being treated. The following are typical doses prescribed for adults and adolescents weighing more than 45 kg:

Treatment of sexually transmitted infections in adults: the usual recommended dose is 1 g of azithromycin given in a single dose;
Treatment of other types of infections in adults: the typical dose is 500 mg per day for 3 days, taken at the same time each day (for a total of 1500 mg over the course of 3 days), as directed by your healthcare provider. Alternatively, the same 1500 mg dose can be given over the course of 5 days, with 500 mg taken the first day followed by 250 mg per day on days 2 through 5.

For children and adolescents weighing less than 45 kg, doses should be calculated by a pediatrician based on weight.

In general, the total dose prescribed for children is 30 mg/kg, administered as 10 mg/kg per day for 3 days. Alternatively, a 5-day course may be prescribed consisting of an initial dose of 10 mg/kg on the first day followed by 5 mg/kg given once a day on days 2 through 5.

The pediatrician may recommend administering a single dose of 30 mg/kg for the treatment of acute otitis media in children. Doses should not exceed 500 mg per day.

It is important to take azithromycin as directed by your doctor. In some cases, a doctor or other healthcare provider may prescribe a different dose than those listed above. Azithromycin should not be given to anyone without a clear indication, as unnecessary treatment with azithromycin can contribute to bacterial resistance and other complications.

2. Children's azithromycin

Children's azithromycin comes in the form of a powder for suspension containing 300, 600, 900, or 1200 mg of azithromycin per bottle. It should be diluted before use to a 200 mg/5 mL syrup. (Note: the 300 mg azithromycin is diluted to a concentration of 100 mg/5 mL.)

Doses will vary based on body weight and the condition being treated. The following table provides the typical doses for the treatment of strep throat in children, using azithromycin 200 mg/5 mL oral suspension:

Body weight	3-day treatment	5-day treatment
Less than 15 Kg	10 mg/kg once a day	Day 1: 10 mg/kg in a single dose, Days 2-5: 5 mg/kg once daily
15 to 25 Kg	5 mL (200 mg) once a day	Day 1: 5 mL (200 mg) in a single dose, Days 2-5: 2.5 mL (100 mg) once daily
26 to 35 Kg	7.5 mL (300 mg) once a day	Day 1: 7.5 mL (300 mg) in a single dose, Days 2-5: 3.75 mL (150 mg) once daily
36 to 45 Kg	10 mL (400 mg) once a day	Day 1: 10 mL (400 mg) in a single dose, Days 2-5: 5 mL (200 mg) once daily
Greater than 45 Kg	Same as adult dose	Same as adult dose

For adults, elderly persons, and children and adolescents weighing more than 45 kg, the usual dose is 12.5 mL in one daily dose for 3 days, totaling 1500 mg over the course of 3 days. Alternatively, the same dose can be given over 5 days, with a single dose of 12.5 mL given on the first day followed by 6.25 mL per day on days 2 through 5.

For urethritis and cervicitis caused by Chlamydia trachomatis, the dose is 25 mL (1000 mg) given in one single dose.

The dose for the treatment of otitis media in children weighing more than 5 kg should be calculated by a pediatrician based on body weight. The usual recommended dose is 30 mg/kg given in one single dose.

How to prepare the oral suspension

The azithromycin oral suspension comes in the form of a powder and should be diluted before use to a concentration of 200 mg/5 mL. To reconstitute the powder, add water and shake well for at least 1 minute.

The amount of water to add depends on the amount of azithromycin in the bottle:

Azithromycin 600 mg (15 mL bottle): add 9 mL of water
Azithromycin 900 mg (22.5 mL bottle): add 12 mL of water
Azithromycin 1200 mg (30 mL bottle): add 15 mL of water

Note: Azithromycin 300 mg oral suspension should be diluted to a concentration of 100 mg/5 mL and will involve different dosing instructions. To prepare the 300 mg oral suspension, add 9 mL of water.

Azithromycin oral suspension should be administered with the dosing syringe provided in the package. Make sure to always shake the bottle well before use.

After preparing the medication, store at room temperature for a maximum of 5 days. Any leftover medication should be discarded after that time.

Side effects

Common side effects of azithromycin are nausea, vomiting, diarrhea, loose stool, abdominal discomfort, constipation, and excess gas. Dizziness, somnolence, and loss of appetite may also occur.

Azithromycin can also cause a serious allergic reaction requiring immediate medical attention. Stop taking the medication right away and seek emergency help for any signs of an allergic reaction such as difficulty breathing; chest pain; throat closure; swelling of the tongue, lips, or face; hives; or blistering/peeling of the skin.

Does azithromycin interfere with birth control?

Azithromycin does not reduce the effectiveness of birth control, however it can cause intestinal imbalances resulting in diarrhea, which can impact the absorption of birth control pills in the gut. The effects of your birth control may be reduced if you experience diarrhea within 4 hours of taking your birth control pill.

Contraindications

Azithromycin should not be used by people with an allergy to azithromycin or any of its components. Before taking azithromycin, be sure to tell your doctor if you are pregnant or breastfeeding.

Azithromycin is not recommended for people with liver or kidney disease or in those with cardiovascular defects, as these conditions can alter the absorption and metabolism of this medication and lead to serious side effects.