Azithromycin (Zithromax®) for Chlamydia

Azithromycin is a powerful broad spectrum semi-synthetic macrolide antibiotic. It is the first representative of a new subclass of macrolides called azalides.

Azithromycin is used to treat the following 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).
  • 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.

Azithromycin (Zithromax) Efficacy for Chlamydia

In the United States, genital Chlamydia trachomatis is a prevalent sexually transmitted infection. Rate of chlamydial infection is highest among persons younger than 25 years.

Chlamydia trachomatis is an intracellular bacteria that shares properties of both viruses and bacteria. Chlamydia is very insidious asymptomatic or "silent" infection. The most serious consequences of untreated chlamydia include Pelvic inflammatory disease (PID), ectopic pregnancy, infertility, and Reiter’s syndrome. In men prolonged chlamydia infection can lead to epididymitis. In women, there is an increased risk of upper reproductive tract damage with re-infection. In pregnant woman, chlamydia can contribute 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 chlamydia infection, the cure rate being of 98%3. The very good tolerance and the high compliance makes this antibiotic the first choice in the treatment of Chlamydia trachomatis.

Azithromycin produces prolonged effect, concentrates intracellularly, and achieves very high levels in the uterine and cervical tissue for 20 days or more. The high prolonged concentration of azithromycin in gynaecological tissues ensures the presence of antibiotic throughout the long life cycle of Chlamydia trachomatis.

Chlamydia during pregnancy
Azithromycin has been proven to be safe and effective for chlamydia during pregnancy5.


Azithromycin dosage for Chlamydia treatment is 1.000 mg orally as a single dosage. According to the Sexually Transmitted Diseases Treatment Guidelines, 20061, this regimen cures the infection and usually eliminates the symptoms.

You should stop having sex until begin the treatment and avoid sexual activity for the next 7 days after taking the antibiotic.

Recent studies suggest, that longer course of azithromycin therapy may result in lower rate of recurrent infections10.

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.


  • Azithromycin continues to be a recommended first-line regimen for uncomplicated chlamydial infections.
  • One of the most effective antibiotics for Chlamydia. Urogenital Chlamydia trachomatis is highly susceptible to azithromycin 2, 6.
  • Although not approved by the FDA for use in pregnancy, azithromycin appears to be safe and effective for Chlamydia during pregnancy.
  • Single-dose therapy is very attractive because it minimizes treatment failure from lack of medication adherence.
  • Targeted activity from the site of infection. Azithromycin achieves high concentration in phagocytes and is effectively transported the site of infection.
  • Low potential for drug interactions. Since 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 once daily antibiotic regimen ensures good patient's adherence. 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 promotes treatment success, decreases development of antibiotic-resistant bacteria, and decreases need for subsequent represcribing of antibiotics.
  • Excellent safety - rarely causes side effects. Azithromycin offers perfect tolerability, with a low rate of negative effects.


  • According to the FDA warning issued in 2013, azithromycin can cause potentially life-threatening arrhythmias7. Patients with known QT interval abnormalities, or who take medications to treat arrhythmias, should be treated with doxycycline instead.
  • Azithromycin is less effective than doxycycline for the treatment of rectal chlamydial infections8. It is possible that the concentration of azithromycin in rectal tissue is lower than that in urethral or cervical tissue9.


  • 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).

Mechanism of action

By inhibition of RNA-dependent protein synthesis azithromycin 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. As a result, administration is very simple and short.

Reviews, Discussion Boards & Forums


  • 1. 2006 STD Treatment Guidelines, developed by CDC
  • 2. Hong KC, Schachter J, Moncada J, Zhou Z, House J, Lietman TM. Lack of macrolide resistance in Chlamydia trachomatis after mass azithromycin distributions for trachoma. Emerg Infect Dis. 2009 Jul;15(7):1088-90
  • 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
  • 5. Pitsouni E, Iavazzo C, Athanasiou S, Falagas ME. Single-dose azithromycin versus erythromycin for Chlamydia trachomatis infection during pregnancy: a meta-analysis of randomised controlled trials. Int J Antimicrob Agents. 2007 Sep;30(3):213-21. PubMed
  • 6. Ljubin-Sternak S, Mestrovic T, Vilibic-Cavlek T, Mlinaric-Galinovic G, Sviben M, Markotic A, Skerk V. In vitro susceptibility of urogenital Chlamydia trachomatis strains in a country with high azithromycin consumption rate. Folia Microbiol (Praha). 2013 Sep;58(5):361-5. PubMed
  • 7. FDA Drug Safety Communication: Azithromycin (Zithromax or Zmax) and the risk of potentially fatal heart rhythms.
  • 8. Khosropour CM, Dombrowski JC, Barbee LA, Manhart LE, Golden MR. Comparing azithromycin and doxycycline for the treatment of rectal chlamydial infection: a retrospective cohort study. Sex Transm Dis. 2014 Feb;41(2):79-85. PubMed
  • 9. Hocking JS, Kong FY, Timms P, Huston WM, Tabrizi SN. Treatment of rectal chlamydia infection may be more complicated than we originally thought. J Antimicrob Chemother. 2015 Apr;70(4):961-4.
  • 10. Horner PJ. Azithromycin antimicrobial resistance and genital Chlamydia trachomatis infection: duration of therapy may be the key to improving efficacy. Sex Transm Infect. 2012 Apr;88(3):154-6.

Written by, October 2009.
Last updated: November, 2015

Interesting facts


  • Generic name: Azithromycin
  • Trade names: Zithromax, Z-pak, Sumamed (Pliva)
  • Pharmacologic category: Macrolide antibiotic
  • FDA approved: June 12, 1996
  • Pregnancy risk factor: B
  • Macrolides are an old and well-established class of antibiotics that have long played an vital role in the treatment of infectious diseases.
  • 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 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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