Zithromax dosage, forms, and strengths

Zithromax (azithromycin) is a type of macrolide antibiotic developed by the pharmaceutical company Pfizer. It is approved by the United States Food and Drug Administration (FDA) for the treatment of a variety of bacterial infections. The antibiotic works by interfering with the protein synthesis of bacteria on its cell wall. This ultimately stops the growth of the bacteria it is targeting. 

Common bacterial infections treated with Zithromax include diseases found in the respiratory system, skin, ear, or for the treatment of sexually transmitted infections. Other common brand names for this antibiotic include Zmax and Z-Pak. The generic name is azithromycin. Zithromax is usually taken by mouth or given as an injection.

RELATED: What is a Z-Pak?

Zithromax forms and strengths

Dosage forms for Zithromax include solutions, tablets, capsules, packets, or powders. Here are the various forms available for this prescription antibacterial medication:

• Tablets: 250 milligrams (mg), 500 mg, or 600 mg

• Capsules: 250 mg and 500 mg

• Oral suspension: 100 mg or 200 mg per 5 milliliters (mL)

• Packet: 1 gram (g) per packet

• Powder: 500 mg or 25 g injection, lyophilized powder for reconstitution

Zithromax dosage for adults

Zithromax is approved for the management of a variety of infectious diseases. Here is a list of the types of medical conditions Zithromax can treat:

• Acute bacterial sinusitis

• Babesiosis

• Bacterial infection

• Bronchitis

• Cervicitis

• Chancroid

• COPD

• Chlamydia trachomatis

• Clostridium difficile Infection

• Cystic fibrosis 

• Gonorrhoeae infection

• Endocarditis

• Haemophilus influenzae

• Lyme disease

• Mycobacterium avium complex (MAC) infection

• Nongonococcal urethritis

• Acute otitis media

• Pertussis

• Pharyngitis

• Community acquired pneumonia

• Skin infection

• Staphylococcus aureus infections

• Streptococcal infection

• Streptococcus pneumoniae

• Syphilis

• Tonsillitis

* There are several off-label treatments for other health conditions that are NOT listed.

Zithromax dosage for uncomplicated, acute bacterial infections

Zithromax is approved for the treatment of acute bacterial infections due to Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae.

• Start with 500 mg tablet once on day one, followed by a daily dose of a 250 mg tablet for four days

Zithromax dosage for gonococcal and nongonococcal urethritis or cervicitis 

Zithromax is approved for the treatment of urethritis and cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae.

• Take 1 gm tablet once

Zithromax dosage for chancroid (genital ulcer)

Zithromax is approved for the treatment of chancroid due to Haemophilus ducreyi in men only.

• Take 1 gm tablet once

Zithromax dosage for PID

Zithromax is approved for the treatment of PID due to Chlamydia trachomatis, Neisseria gonorrhoeae, or Mycoplasma hominis.

• Start with 500 mg IV daily for one to two days, followed by a 250 mg tablet daily for five to six days

Zithromax dosage for community acquired pneumonia

Zithromax is approved for the treatment of community acquired pneumonia due to Chlamydophila pneumonia, Legionella pneumonia, Haemophilus influenzae, Mycoplasma pneumonia, or Streptococcus pneumonia.

• Start with 500 mg tablet once on day one, followed by a daily dose of a 250 mg tablet for four days

Zithromax dosage for COPD exacerbation

Zithromax is approved for the treatment of acute bacterial COPD exacerbation as well as the prevention of this condition.

• Acute bacterial COPD exacerbation: Start with 500 mg tablet once on day one followed by a daily dose of a 250 mg tablet for four days

• COPD exacerbation prevention: Take one 250 mg tablet once (off-label treatment)

Zithromax dosage for pharyngitis/tonsillitis

Zithromax is approved for the treatment of Streptococcal pharyngitis or tonsillitis. 

• Start with 500 mg tablet once on day one, followed by a daily dose of a 250 mg tablet for four days

  • Z-pak is taken for six days with 250 mg tablets

  • Tri-pak is taken for three days with 500 mg tablets 

Zithromax dosage for MAC infection

Zithromax is approved for the treatment of disseminated MAC infections as well as the prevention of this condition.

• MAC treatment: Start 500-600 mg orally daily plus ethambutol

• MAC prevention: Take 1200 mg orally once a week

Zithromax dosage for COVID-19

Zithromax is under investigation for a potential treatment protocol for patients diagnosed with COVID-19 as clinical trials are underway. Currently there is no dose of azithromycin approved by the FDA as its effectiveness against COVID-19 has not been proven.

Zithromax dosage for children

Zithromax is approved for children for a variety of infections. Pediatric dosing may vary by age and weight, depending on the condition being treated.

Zithromax dosage for pediatric acute otitis media

Zithromax is approved for the treatment of mild to moderate acute middle ear infections due to Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae. Approved for those greater than 6 months of age. 

• Take 30 mg/kg orally once, OR

• 10 mg/kg (maximum: 500 mg/dose) orally daily for three days, OR

• 10 mg/kg (maximum: 500 mg/dose) orally on day one, followed by 5 mg/kg (maximum: 250 mg/dose) orally daily for four days 

Zithromax dosage for pediatric community acquired pneumonia

Zithromax is approved for the treatment of community acquired pneumonia due to Chlamydophila pneumonia, Legionella pneumonia, Haemophilus influenzae, Mycoplasma pneumonia, or Streptococcus pneumonia. Approved for those greater than 6 months of age.

• 10 mg/kg orally once on day one, followed by 5 mg/kg orally daily for four days 

• Extended-release: 

  • Less than 34 kg: 60 mg/kg (maximum dose: 2 g/dose) orally as a single dose

  • Greater than 34 kg: 2 g orally as a single dose

• 16 years and older: 

  • 500 mg IV once a day as a single dose for at least two days, followed by 500 mg (immediate-release form) orally for seven to 10 days

Zithromax dosage for pediatric pharyngitis/tonsillitis

Zithromax is approved for the treatment of Streptococcal pharyngitis or tonsillitis when first-line treatment is not an option such as those with penicillin allergies. Approved for those older than 2 years of age. 

• Start with 12 mg/kg orally daily for five days; not to exceed 500 mg/day

Zithromax dosage restrictions

Caution is advised when prescribing Zithromax for patients with renal or liver impairment. Patients with renal impairment that have a creatinine clearance greater than 10 mL/min do not require any dose adjustment. If severe renal disease exists, the medication should be used with caution. Patients who are on dialysis also do not require any adjustments or supplements. Those who have ever experienced jaundice or liver problems from using azithromycin in the past, should not be prescribed this medication again. 

You should not take Zithromax if there has been a known allergic reaction to similar macrolide antibiotics such as erythromycin or clarithromycin. You should discuss with your healthcare provider if you have any of the following conditions before starting Zithromax:

• Heart abnormalities

• History of long QT intervals in the heart

• Myasthenia gravis

• Low potassium levels

• Kidney disease

• Liver disease

Seniors older than the age of 75 should also be cautioned against the use of Zithromax as there is a higher risk of developing torsades de pointes arrhythmias.

Zithromax dosage for pets 

Zithromax is a prescribed medication that may be used for the treatment of a variety of bacterial, rickettsial, and parasitic infections in dogs and cats. This medication is not FDA-approved for use in animals but may be prescribed by a veterinarian for off-label use. 

• Standard dosage in dogs: 2.5 to 5 mg per pound orally daily for seven days.

• Standard dosage in cats: 2.5 to 7.5 mg per pound orally once or twice a day for seven days.

RELATED: When does your pet need antibiotics?

How to take Zithromax

• Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

• Multiple-dose Zithromax oral liquid or tablets: You may take this medicine with or without food. Shake the bottle well before you measure the medicine. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.

• Single-dose extended-release oral liquid: Take this medicine on an empty stomach at least one hour before you eat, or two hours after you eat. Call your doctor for medical advice if you vomit within one hour after you take the medicine. You must take the liquid within 12 hours after the pharmacist gives it to you. Shake the bottle well before you measure the medicine. Measure your dose with a marked measuring spoon, cup, or syringe.

• Single-dose extended-release powder: Open one packet and pour all of the medicine into a glass with about 2 ounces (¼ cup) of water. Mix well and drink the medicine right away. Pour another 2 ounces of water into the same glass, and drink the remaining medicine.

• Extended-release oral liquid: Do not refrigerate or freeze.

• Oral liquid for one dose only: Store at room temperature. Do not store in the refrigerator or allow the medicine to freeze.

• Injection route: A nurse or other health provider will give you this medicine.

• Your doctor will tell you how much medicine to use. Do not use more than directed.

• Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

• Store the medicine in a closed container at room temperature or in the refrigerator, away from heat, moisture, and direct light. Use it within 10 days of filling the prescription.

• Your doctor may give you a few doses of this medicine until your condition improves, and then you may be switched to an oral medicine that works the same way. Talk to your doctor if you have any concerns about this.

Zithromax dosage FAQs

What happens if I miss a dose of Zithromax?

It is important that you take Zithromax as directed. Do not take more of the medication if a dose is missed. Take the missed dose as soon as possible but you may skip the dose if the next scheduled dose is near.

Can you overdose on Zithromax?

Taking too much Zithromax may cause potential overdose. The following serious adverse reactions require immediate medical attention:

• Angioedema

• Allergic reaction

• Jaundice

• Hepatitis

• Pancreatitis

• Infantile hypertrophic pyloric stenosis

• Stevens-Johnson syndrome

• Toxic epidermal necrolysis

• Clostridium difficile diarrhea

• QT prolongation

• Torsades de pointes

• Myasthenia gravis exacerbation

Some common side effects of azithromycin that should also be monitored closely include:

• Gastrointestinal symptoms (vomiting, diarrhea, nausea)

• Vaginitis

• Abdominal pain especially in the upper quadrant

• Dizziness

• Rash

• Flatulence

• Headache

• Loss of appetite

• Itching

• Impaired hearing with high-dose usage

RELATED: How to prevent a yeast infection from antibiotics

What interacts with Zithromax?

It is important that antacids are not taken two hours prior or after taking Zithromax—especially those containing magnesium and aluminum. These medications can reduce the effectiveness of this antibacterial.

Drug interactions causing serious adverse reactions may occur when combining Zithromax. If you are taking the following medications, please review them with your healthcare provider as close monitoring or dose adjustments may be required:

• Colchicine

• Digoxin

• Nelfinavir

• Phenytoin

• Warfarin (brand names: Coumadin, Jantoven)

The following drugs are contraindications with the use of Zithromax:

• Cisapride

• Dronedarone

• Pimozide

• Thioridazine

What happens when you mix Zithromax and alcohol?

There are no known contraindications with the use of alcohol and Zithromax. 

Is it safe to take Zithromax during pregnancy?

Zithromax is safe to use during pregnancy and breastfeeding. Breast milk production is not altered with its use. 

Related resources for Zithromax dosages:

• Adult dosing, Epocrates

• Azithromycin for COVID-19, JAMA Network

• Pediatric dosing, Epocrates

• Azithromycin (Zithromax®) for Cats and Dogs, PetPlace

• Drug interactions, Epocrates