Bronchitis & pneumonia, sinusitis & pharyngitis/ tonsillitis, otitis media, skin & soft tissue infections, sexually ransmitted diseases.
Azithromycin is acid-stable and can therefore be taken orally with no need of protection from gastric acids. It is readily absorbed; its absorption is greater on an empty stomach. Time to peak concentration in adults is 2.1 to 3.2 hours for oral dosage forms. Due to the high concentration in phagocytes, azithromycin is actively transported to the site of infection. During active phagocytosis, large concentrations of azithromycin are released. The concentration of azithromycin in the tissues can be over 50 times higher than in plasma. This is due to ion trapping and the high lipid solubility.
Azithromycin's half-life allows a large single dose to be administered and yet maintain bacteriostatic levels in the infected tissue for several days. Following a single 500 mg dose, plasma concentrations of azithromycin declined in a polyphasic pattern with a mean apparent plasma clearance of 630 mL/min and a terminal elimination half life of 68 hours. The prolonged terminal half-life is thought to be due to extensive uptake and subsequent release of drug from tissues. Biliary excretion of azithromycin, predominantly unchanged, is a major route of elimination. Over the course of a week, approximately 6% of the administered dose appears as unchanged drug in urine.
Microbiology: Azithromycin acts by binding to the 50S ribosomal subunit of susceptible microorganisms and, thus, interfering with microbial protein synthesis. Nucleic acid synthesis is not affected. Azithromycin has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections:
Aerobic and facultative gram-positive microorganisms: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes
Aerobic and facultative gram-negative microorganisms: Haemophilus ducreyi, Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae
Other microorganisms: Chlamydia pneumoniae, Chlamydia trachomatis , Mycoplasma pneumoniae , Betalactamase production should have no effect on azithromycin activity.
Aerobic and facultative gram-positive microorganisms: Streptococci (Groups C,F,G), Viridans group streptococci
Aerobic and facultative gram-negative microorganisms: Bordetella pertussis, Legionella pneumophila
Anaerobic microorganisms: Peptostreptococcus species, Prevotella bivia
Adults: 500 mg once daily for 3 days. Children: 10 mg/kg body weight once daily for 3 days.
Antacid: In patients receiving azithromycin and antacids, azithromycin should be taken at least 1 hour before or 2 hours after the antacid. Carbamazepine: In a pharmacokinetic interaction study in healthy volunteers, no significant effect was observed on the plasma levels of carbamazepine or its active metabolite.
Cyclosporin: Some of the related macrolide antibiotics interfere with the metabolism of cyclosporin. In the absence of conclusive data from pharmacokinetic studies or clinical data investigating potential interactions between azithromycin and cyclosporine, caution should be exercised before co-administration of these two drugs. If coadministrations is necessary, cyclosporin levels should be monitored and the dose adjusted accordingly.
Digoxin: Some of the macrolide antibiotics have been reported to impair the metabolism of digoxin (in the gut) in some patients. Therefore, in patients receiving concomitant azithromycin and digoxin the possibility of raised digoxin levels should be borne in mind and digoxin levels monitored.
Ergot derivatives: Because of the theoretical possibility of ergotism, azithromycin and ergot derivatives should not be co-administered.
Methylprednisolone: In a pharmacokinetic interaction study in healthy volunteers, azithromycin had no significant effect on the pharmacokinetics of methylprednisolone.
Theophylline: There is no evidence of any pharmacokinetic interaction when azithromycin and theophylline are co-administered to healthy volunteers. In general, however, theophylline levels should be monitored.
Warfarin: In a pharmacodynamic interaction study, azithromycin did not alter the anticoagulant effect of a single 15 mg dose of warfarin administered to healthy volunteers. Azithromycin and warfarin may be co-administered, but monitoring of the prothrombin time should be continued as routinely performed.
Terfenadine: Azithromycin did not affect the pharmacokinetics of terfenadine administered at the recommended dose of 60 mg every 12 hours. Addition of azithromycin did not result in any significant changes in cardiac repolarisation (QTc interval) measured during the steady state dosing of terfenadine.
Known hypersensitivity, should not be used in patients with hepatic disease. Avoid concomitant administration with terfenadine or astemizole. Precaution should be taken in patients with more severe renal impairment.
Nausea, vomiting, abdominal discomfort (pain/cramps), flatulence, diarrhoea, headache, dizziness & skin rashes, reversible elevations in liver transaminases.
The initial treatment of chlamydial cervicitis in pregnancy. In other infections, Azithromycin should be used only when clearly needed. Exercise caution when administering to a nursing woman.
There is no data on overdosage with Azithromycin. Typical symptoms of overdosage with macrolide antibiotics include hearing loss, severe nausea, vomiting and diarrhoea. Gastric lavage and general supportive measures are indicated.
Keep in a dry place away from light and heat. Keep out of the reach of children.
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