Azithromycin (Zithromax)

Azithromycin (Zithromax)

Dose and Administration

Adults: Give 500 mg orally on day 1 followed by 250 mg once a day for a total of 5 days. For the prevention of disseminated Mycobacterium avium complex disease, the recommended oral dose is 1200 mg taken once weekly. For urethritis or cervicitis due to Chlamydia trachomatis, 1 g should be taken orally as one dose.
The IV form should be administered as 500 mg IV once daily followed by oral therapy for completion of therapy.
Pediatrics: Usual dose is 10 mg/kg for 5 days.

Azithromycin (Zithromax) Uses

FDA-approved: Treatment of mild to moderate cases of the following infections: acute bacterial exacerbation of chronic bronchitis due to Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae; community acquired pneumonia due to 5. pneumoniae or H. influenzae; pharyngitis/tonsillitis due to Streptococcus pyogenes; acute otitis media due to H. influenzae, M catarrhalis, or 5. pneumoniae;

uncomplicated skin and skin structure infections due to Staphylococcus aureus, S. pyogenes, or Streptococcus agalactiae; and nongonococcal urethritis and cervicitis due to C. trachomatis. It is also approved for the prevention of disseminated Mycobacterium avium complex disease in HIV-infected patients. The IV form is approved for community acquired pneumonia due to C. pneumoniae, H. influenzae, L. pneumophila, M. catarrhalis, M. pneumoniae, S. aureus, or 5. pneumoniae and pelvic inflammatory disease due to C. trachomatis, N. gonorrhoeae, or M. hominis in patients who require initial intravenous therapy. Another use is chancroid.

Azithromycin (Zithromax) Pharmacology

Azithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis in susceptible organisms by reversibly binding to the 50S ribo-somal subunit. Based on similar mechanisms of action, azithromycin should not be combined with clindamycin or chloramphenicol to prevent antibacterial antagonism. Its spectrum of activity is expanded as compared to erythromycin. It retains similar gram-positive activity (e.g., S. pyogenes, S. pneumoniae, S. aureus); however, it has greater gram-negative activity than erythromycin or clarithromycin. Susceptible gramnegative organisms include Neisseria meningitidis, N. gonorrhoeae, Haemophilus ducreyi, H. influenzae, M. catarrhalis, and Bordetella pertussis. Azithromycin also exerts activity against Treponema pallidum, Mycoplasma pneumoniae, Legionella pneumophila, Chlamydia species, and Mycobacterium avium complex.
Azithromycin is more acid stable than erythromycin. The capsule formulation should be taken on an empty stomach to maximize absorption, whereas the tablet and suspension may be taken with or without food. It is widely distributed throughout the body and concentrations in pulmonary macrophages, polymorphonuclear leukocytes, and genital/ pelvic tissues remain increased for several days following administration. Penetration of the cerebral spinal fluid is negligible and therefore it should not be used to treat infections of the central nervous system. Azithromycin is excreted primarily in the feces.

Azithromycin (Zithromax) Adverse Effects/Precautions

The most common adverse effects involve the gastrointestinal tract and include nausea, vomiting, diarrhea, and abdominal pain. Serious allergic reactions have occurred rarely with azithromycin. Reversible elevations in liver function tests may occur. Pregnancy category B.

Azithromycin (Zithromax) Drug Interactions

Azithromycin does not affect the cytochrome P450 system unlike erythromycin and clarithromycin. When combined with warfarin, however, cases of increased prothrombin times and INRs have been reported. Therefore if azithromycin is combined with warfarin, close monitoring should be performed.

Special Considerations

Administration with food may lessen the gastrointestinal adverse effects. The oral suspension single packets should be mixed with 60 mL of water and taken immediately. The glass should be mixed with an additional 60 mL of water and ingested to ensure the entire dose is consumed.