Azithromycin (Zithromax)

• Generic name: Azithromycin
• Trade names: Zithromax, 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 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).

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

Asymptomatic or "silent" condition is very insidious. 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.

According to the Sexually Transmitted Diseases Treatment Guidelines, 20061, the following regimen cures the infection and usually eliminates symptoms:
Azithromycin 1 g orally once.

The high sustained concentrations in gynecologic tissue result in the presence of azithromycin throughout the long life cycle of Chlamydia trachomatis.

• 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.

• 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.

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.

• Ratings and comments for Azithromycin on AskaPatient.com
• Azithromycin News on Topix.com
• Zithromax user ratings and reviews on RevolutionHealth
• Zithromax reviews about success rate on DailyStrength.org
• Reviews, Ratings by Patients on DrugLib.com
• Azithromycin User Reviews for sinusitis (user's rating - 8.0 points), bronchitis (user's rating - 8.4 points) on Drugs.com

• 1. 2006 STD Treatment Guidelines, developed by CDC
• 2. Fernandez-Obregon AC. Int J Dermatol. 2000 Jan;39(1):45-50. PubMed