Mild to moderate low respiratory tract infections and upper respiratory tract infections and uncomplicated skin and and soft tissue infections.

Adults(>16 years of age) : 500 mg as a single dose on the first day followed by 250 mg once daily on days 2 through 5 for a total dose of 1.5 g or 500 mg once daily for 3 days.

Genital ulcer disease due to Haemophilus ducreyi (chancroid),non-gonococcal urethritis and cervicits due to chlamydia.

Adults(>16 years of age) :Single 1g (1000 mg) dose of azithromycin.

Urethritis and cervicities due to Neisseria gonorrhoeae.

Adults(>16 years of age) :Single 2g (2000 mg) dose of azithromycin.

Childrens(<16 years of age) : The usual dose for children is 10 mg/kg body weight orally, once a day for 3 days. Alternatively after a 10 mg/kg body weight of oral loading dose on the first day, the therapy can be continued at a dose of 5 mg/kg body weight on four subsequent days. (The drug is not recommended for use in infants below six months of age).

(ii) THERAPEUTIC / DIAGNOSTIC CLAIMS

Azithromycin 250 is indicated in the treatment of:
Lower respiratory tract infections: Community acquired pneumonia, acute bacterial exacerbations of chronic obstructive pulmonary disease, acute bronchitis due to Haemophilus influenzae, Moraxella catarrhalis or Streptococcus pneumonia.
Upper respiratory tract infections, Ear, nose and throat infections like Tonsillitis, sinusitis, otitis media and pharyngitis
Genitourinary tract infections (including sexually transmitted diseases) Urethritis, prostatitis. cervicitis, cervico-vaginitis and salpingitis due to N. gonorrhoeae and C. trachomatis,
Chlamydial conjunctivitis.
Skin and soft tissue infections: Folliculitis, furuncles, carbuncles, impetigo, pyoderma, infected ulcer, infected dermatitis, cellulitis and erysipelas due to S. aureus, S. pyogenes or S. agalactiae

(iii) DESCRIPTION OF DOSAGE FORM

Azithromycin is an azalide antibiotic, subclass of the macrolides. Chemically it is derived by insertion of a nitrogen atom into the lactone ring of erythromycin A. The unique chemistry endows it with improved pharmacokinetic properties, improved tolerance and compliance.
Azithromycin acts by binding to the 50s ribosomal subunits of susceptible organisms and thus interferes with microbial protein synthesis.

WARNING AND PRECUATION :
Serious allergic reactions including angioedema, anaphylaxis and dermatological reactions including Stevens Johnson Syndrome and toxic epidermal necrolysis have been reported rarely in patients on Azithromycin therapy.
If an allergic reaction occurs, the drug should be discontinued and appropriate therapy should be instituted. Physicians should be aware that reappearance of the allergic symptoms may occur when symptomatic therapy is discontinued.
Pseudomembranous colitis has been reported with nearly nearly all antibacterial agents and may range in severity from mild to life threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.
Precautions: See Drug Interaction

DRUG INTERACTIONS:
Aluminium and Magnesium containing Antacids: Aluminium and Magnesium containing antacids reduce the peak serum levels(rate) but not the AUC (extent)of orally administered azithromycin. Patients should be cautioned not to take Aluminium and Magnesium containing antacids and Azithromycin by the oral route simultaneously.
Theophylline: Azithromycin did not affect the plasma level pharmocokinetics of theophylline administered as a single IV dose. However concurrent use of macrolides and theophylline has been associated with increase in serum concentrations of theophylline. Therefore, until further data are available, carefully monitor plasma theophylline levels in patients receiving Azithromycin concomitantly.
Warfarin: Azithromycin did not affect the prothrombin time response to a single dose of warfarin. However, concurrent use of macrolides and warfarin has been associated with increased anticoagulant effects. Carefully monitor prothrombin time in all patients treated with azithromycin and warfarin concomitantly.
The following drug interactions have not been reported in clinical trails with Azithromycin however no specific drug interaction studies have been performed to evaluate drug-drug interactions. Nonetheless, they have been observed with macrolide products. Until further data are developed regarding drug interactions when azithromycin and these drugs are used concomitantly, careful monitoring of patients is advised.
Digoxin: Elevated digoxin levels.
Ergotamine or dihydroergotamine; Acute ergot toxicity characterized by severe peripheral vasospasm and dysesthesia.
Trizolam: Increased pharmacological effect of trizolam by decreasing the clearance of trizolam.
Drugs metabolized by the cytochrome P450 system: Elevations of serum carbamazepin, terfenadine, cyclosporin, hexobarbital and phenytoin levels

USE IN PREGNANCY AND NURSING MOTHERS
Teratogenic Effects: Pregnancy Category B. There are no adequate and well-controlled studies in pregnant women. Azithromycin should be used in pregnancy only if clearly indicated.
Lactation:
It is not known whether Azithromycin is excreted in human milk. Because many drugs are excreted in milk; caution should be exercised when Azithromycin is administered to a nursing mother.

(iv) CONTRAINDICATIONS

Azithromycin is contraindicated in patients with a history of allergic reactions to azithromycin or any other macrolide antibiotics.

(v) SIDE EFFECTS

Azithromycin is well tolerated with a low inidence of side effects in both adults and children. The majority of side effects were gastrointestinal in origin, with diarrhea, abdominal discomfort, nausea, vomiting and flatulence.
Occasionally reversible elevations in liver transaminases have been seen. Allergic reactions like skin rash may occur.

( vi ) TOXIC EFFECT:

Mutagenicity, Carcinogenecity and Teratogenecity
Animal reproduction studies have demonstrated that azithromycin crosses the placenta, but it has shown no teratogenic potential. No carcinogenicity was evident in routine toxicology tests with treatment periods of up to 6 months. No data are available for longer periods of treatment. In high–dose animal studies, giving drug doses 40 fold higher than those expected in clinical practice, azithromycin was noted to cause reversible phospholipidosis, a phenomenon characterised by ultramicroscopic lamellated structures in the lysosomes of various tissues. Its significance in humans is unknown and there is no evidence that this is of relevance to the normal use of azithromycin in humans.
Azithromycin was not mutagenic in several in vitro tests, including the mouse lymphoma assay, human lymphocyte clastogenic assay, and mouse bone maroow clastogenic assay.

Acute Toxicity
Limited information is available on the acute toxicity of azithromycin. The acute lethal dose of the drug in humans is not known. The oral Lethal Dose if azithromycin.in mice and rats is 3000-4000 mg/kg.