Azithromycin is an azalide antibiotic, subclass of the macrolide class of antibiotics. Azithromycin acts by binding to the 50s ribosomal subunit of susceptible organisms and thus interferes with microbial protein synthesis.
Azithromycin demonstrated activity in vitro, against a wide range of gram-positive and gram-negative bacteria including: Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes (Group A) and other Streptococcal species; Haemophilus influenzae and parainfluenzae; Moraxella catarrhalis; anaerobes including Bacteroides fragilis, Escherichia coli, Bordetella pertussis, Bordetella parapertussis, Borrelia burgdorferi, Haemophilus ducreyi, Neisseria gonorrhoeae and Chlamydia trachomatis. Azithromycin also demonstrates activity in vitro against Legionella pneumophila, Mycoplasma pneumoniae and hominis; Campylobacter sp., Toxoplasma gondii and Treponema pallidum.
Oral or Injection:
Adults or elderly:
- For lower respiratory tract infections including bronchitis and pneumonia, upper respiratory tract infections including sinusitis and pharyngitis / tonsillitis, otitis media and skin and soft tissue infections: The total dose of Azithromycin is 1.5 gm given as 500 mg once daily for 3 days. An alternative to this dosage schedule is that 500 mg once daily on day 1, followed by 250 mg once daily for next 4 days.
- For sexually transmitted diseases caused by Chlamydia trachomatis: The dose of Azithromycin is 1 gm given as a single dose. Alternatively, 500 mg once daily on day 1, followed by 250 mg once daily for next 2 days may also be given.
Children: The dose of Azithromycin in children over 6 months of age is 10 mg/kg body weight once daily for 3 days. Alternatively, 10 mg/kg on day 1, followed by 5 mg/kg for next 4 days is also recommended. There is no information on use of Azithromycin on children under 6 months of age. For children the dose of Azithromycin suspension is as follows:
- 5-10 kg (6 months-2 years): 1.25 ml – 2.5 ml (¼ – ½ tsp) Once daily for three days
- 11-20 kg (3-8 years): 5 ml (1 tsp) Once daily for three days
- 21-30 kg (9-12 years): 7.5 ml (1 ½ tsp) Once daily for three days
- 31-40 kg (13-15 years): 10 ml (2 tsp) Once daily for three days
- 41-45 years (16-17 years): 11.5 ml (2 ½ tsp) Once daily for three days
- Adult: Instill 1 drop in the affected eye(s) twice daily, eight to twelve hours apart for the first two days and then instill 1 drop in the affected eye(s) once daily for the next five days.
- Pediatric Use: The safety and effectiveness of Azithromycin solution in pediatric patients below 1 year of age have not been established. The efficacy of Azithromycin in treating bacterial conjunctivitis in pediatric patients one year or older has been demonstrated in controlled clinical trials
- Geriatric Use: No overall differences in safety or effectiveness have been observed between elderly and younger patients.
Antacids: Peak serum levels but not the total extent of absorption are reduced by aluminium and magnesium containing antacids in the stomach. Azithromycin should therefore be taken at least 1 hour before or 2 hours after taking these antacids.
Ergot Derivatives: Because of the theoretical possibility of ergotism, concomitant administration of ergot derivatives and Azithromycin should be avoided. Digoxin & Cyclosporin: Macrolides have been known to increase the plasma concentration of Digoxin & Cyclosporin and so caution should be exercised while co-administration is necessary. Anti-
Histamines: A potentially life threatening interaction between erythromycin and terfenadine or astemizole have been reported. Although such an interaction with Azithromycin is not established yet, it is wise to avoid concomitant use of Azithromycin and terfenadine or astemizole.