Azithromycin (Zithromax)

  • Generic name: Azithromycin
  • Trade names: Zithromax, Sumamed (Pliva)
  • Pharmacologic category: Macrolide antibiotic
  • FDA approved: June 12, 1996
  • Pregnancy risk factor: B
Medical uses

Macrolides are an old and well-established class of antibiotics that have long played an essential role in the chemotherapy of infectious diseases.

Azithromycin is a powerful broad spectrum semi-synthetic macrolide antibiotic. It is the first representative of a new subclass of macrolides called azalides. Its chemical structure is similar to that of erythromycin.

Azithromycin is used to treat the following mild to moderate infections:

  • Lower Respiratory Tract infections: acute bacterial exacerbations of chronic obstructive pulmonary disease; community-acquired pneumonia of mild severity.
  • Upper Respiratory Tract infections: pharyngitis, tonsillitis, otitis media, sinusitis
  • Skin and Skin Structure infections (uncomplicated). Abscesses usually require surgical drainage.
  • Chancroid (genital ulcer disease in men): due to the small number of women included in clinical trials, the efficacy of azithromycin in the treatment of chancroid in women has not been established.
  • Sexually Transmitted Diseases: urethritis and cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae.
  • Mycobacterial Infections.

Azithromycin rarely causes side effects. Gastrointestinal disturbances (flatulence, nausea, vomiting, diarrhea and abdominal cramps) and a rash may occur. Transient moderate elevations of hepatic enzymes values, neutropenia and rarely neutrophilia and eosinophilia have been observed.

  • Elimination half-life: The t 1/2 is approximately 68 h.
  • Metabolism: Hepatic
  • Excretion: Excreted primarily unchanged in the bile. Approximately 6% is excreted unchanged in urine (oral); approximately 11% is excreted in the urine after first dose and 14% after fifth (IV).
Azithromycin (Zithromax) for Chlamydia

In the United States, genital Chlamydia trachomatis is a widespread sexually transmitted infection, and the prevalence is highest in persons younger than 25 years.

Chlamydia is very insidious asymptomatic or "silent" condition. The most serious sequelae of untreated chlamydia include PID, ectopic pregnancy, and infertility. In men prolonged chlamydia can lead to epididymitis. In women, there is an increased risk of upper reproductive tract damage with re-infection. In pregnant woman, chlamydia can lead to spontaneous abortion (miscarriage).

Besides frequently not causing any symptoms, Chlamydia trachomatis is very difficult to culture.

How effective is Azithromycin for curing Chlamydia?
Azithromycin is one of the most effective treatments for uncomplicated chlamydia infection, the cure rate being of 98%3. The very good tolerance and the high compliance of this antibiotic makes it the first choice in the treatment of Chlamydia trachomatis infection.

Azithromycin produces prolonged effect, and achieves very high concentrations in the uterine and cervical tissue for 20 days or more. The high sustained concentration of azithromycin in gynecologic tissues results in the presence of antibiotic throughout the long life cycle of Chlamydia trachomatis.

Azithromycin dosage for Chlamydia
1 g orally as a single dosage. According to the Sexually Transmitted Diseases Treatment Guidelines, 20061, this regimen cures the infection and usually eliminates the symptoms.

How long does it take Azithromycin to cure Chlamydia?
The time it takes azithromycin to cure chlamydia infection (to get a negative test result) is about 2-3 weeks4.

  • Targeted activity from the site of infection. Due to the high concentration in phagocytes, azithromycin is actively transported to the site of infection.
  • Active against most bacteria causing respiratory tract infections.
  • Low potential for interactions. Due to the fact that azithromycin is not metabolized through P 450 system, it does not affect metabolism of other drugs. However, other macrolides are frequently involved in drug interactions.
  • Very convenient and easy to use. Simple regimen in antibiotic therapy decreases possibility of bad compliance. Azithromycin's half-life allows a large single dose to be administered and yet maintain bacteriostatic levels in the infected tissue for several days. Good compliance improves clinical outcome, decreases possibility of selection for resistance and decreases need for subsequent represcribing of antibiotics.
  • Excellent safety - rarely causes side effects.
  • Effective for chlamydia during pregnancy. Azithromycin has been shown to be safe in pregnant women and is recommended as the treatment of choice for chlamydia during pregnancy.
Unlabeled uses
  • Dental infections.
    Azithromycin is used in patients who are at risk of developing bacterial endocarditis (a serious and potentially fatal heart infection) following dental procedures likely to induce mucosal or gingival bleeding. Such procedures include dental extractions, periodontal surgery, professional cleanings, orthodontic band (not bracket) placement and some other procedures.
  • Acne
    Azithromycin (administered three times a week) produces about 80% reduction in the inflammatory acne lesions2.
Mechanism of action

By inhibition of RNA-dependent protein synthesis it affects the ability of bacteria to replicate and grow. Antimicrobial spectrum includes different Gram - positive, Gram - negative, anaerobic, intracellular and atypical microorganisms. Because of the transport with white blood cells, Azithromycin possesses a unique characteristic - targeted activity at the site of infection. In infected tissues, it achieves high and sustained therapeutic concentrations that last five to seven days after the last dose. Because of that, administration is very simple and short.

Reviews, Discussion Boards & Forums
  • 1. 2006 STD Treatment Guidelines, developed by CDC
  • 2. Fernandez-Obregon AC. Int J Dermatol. 2000 Jan;39(1):45-50. PubMed
  • 3. Lea AP, Lamb HM. Azithromycin. A pharmacoeconomic review of its use as a single-dose regimen in the treatment of uncomplicated urogenital Chlamydia trachomatis infections in women. Pharmacoeconomics. 1997 Nov;12(5):596-611.
  • 4. Martin DH, Mroczkowski TF, Dalu ZA, McCarty J, Jones RB, Hopkins SJ, Johnson RB. A controlled trial of a single dose of azithromycin for the treatment of chlamydial urethritis and cervicitis. The Azithromycin for Chlamydial Infections Study Group. N Engl J Med. 1992 Sep 24;327(13):921-5. PubMed

Last updated: February 10, 2015

Interesting facts


  • On 20 August 2000 in Washington D.C., USA, the American Chemical Society (ACS), a non-profit association of American chemists and chemical engineers and the largest association of scientists in the world organized the "Heroes of Chemistry 2000" ceremony. For their discovery of azithromycin (Sumamed), PLIVA scientists Slobodan Dokic and Gabrijela Kobrehel were named "Heroes of Chemistry", together with representatives from Pfizer which had also contributed to the success of this antibiotic.
  • Azithromycin offers excellent tolerability, with a low rate of negative effects.
  • Azithromycin has to be one of the most convenient antibiotics. The fact that you can also take just a three or one day course makes it particularly popular with parents of children who don't like to take medicine.

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