Azithromycin is an antibiotic useful for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumonia, traveler’s diarrhea, and certain other intestinal infections. It may also be used for a number of sexually transmitted infections including chlamydia and gonorrhea infections.


Molecular Structure

Class of Drug

Antibiotic, Macrolide.

Mechanism of Action

Inhibits RNA-dependent protein synthesis at the level of the 50S ribosome.

Susceptible organisms in vivo: Like erythromicin but less active against gram-positive bacteria and more active against gram­negative bacteria. Better against Hemophilus influenzae and Moraxella catarrhalis. Also useful against Mycobacterium avium-intrace llulare and Helicobacter pylori.


Indications / Dosage / Route

Routes of Administration: Oral and IV.

Condition: Community-acquired pneumonia

Dose: Adults IV 500 mg as single daily dose, at least 2 days. Follow by oral dosing 500 mg/d, 7-10 days.

Condition: Acute pelvic inflammatory disease

Dose: Adults IV 500 mg as single daily dose, 1 or 2 days. Follow by oral dosing 250 mg/d 7 days.

Condition: Mild to moderate acute exacerbation of COPD, community-acquired pneumonia (mild to moderate), pharyngitis/tonsillitis (second- line therapy), uncomplicated skin and skin structure infections

Dose: Adults PO 500 mg as single dose on first day, then 250 mg/d, days 2-5.

Condition: Genital ulcer disease (chanchroid), nongonoccocal urethritis and cervicitis

Dose: Adults PO 1 g as single dose.

Condition: Urethritis and cervicitis (Neisseria gonorrhoeae)

Dose: Adults PO 2 g as single dose. (Note: resistance is a problem.)

Condition: Acute otitis media, community-acquired pneumonia

Dose: Children: Oral suspension 10 mg/kg as single dose on first day, then 5 mg/kg days 2-5. Maximum: 250 mg/d.

Condition: Pharyngitis/tonsillitis

Dose: Children >2 years: Oral suspension 12 mg/kg once daily, days 1-5.

Adjustment of Dosage

Kidney disease: None.

Liver disease: None.

Elderly: None

Pediatric: Safety and efficacy have not been established for children <6 months for treatment of acute otitis media and <2 years for treatment of pharyngitis/tonsillitis.


Food and Drug Interactions

Food: Should be taken on empty stomach, 1-2 hours after meals.

Pregnancy: Category B.

Lactation: No data available. May appear in breast milk. Best to avoid.

Contraindications: Hypersensitivity to macrolide antibiotics.

Warnings / Precautions: Use with caution in patients with hepatic dysfunction

Clinically Important Drug Interactions

> Drugs that decrease effects/toxicity of macrolides: rifampin, antacids (aluminum, magnesium).

> Macrolides increase effects/toxicity of following drugs: oral anticoagulants, astemizole, benzodiazepines, bromocriptine, buspirone, carbamazepine, cisapride, cyclosporine, digoxin, ergot alkaloids, felodipine, grepafloxacin, statins, pimozide, sparfloxacin, tacrolimus.

Adverse Reactions

> Common: None.

> Severe: pseudomembranous colitis, ventricular arrhythmias, nephritis, cholestatic jaundice, angioedema.

Parameters to Monitor

> Signs and symptoms of superinfection, in particular pseudomembranous colitis.

> Signs and symptoms of renal toxicity.

> Signs and symptoms of hearing impairment. Patients with kidney or liver disease are at highest risk.

Further Useful Info

> Azithromycin has the advantage of improved compliance com-pared with erythromycin because of better tolerability, daily dosage, and shorter course of therapy.

> Often used as outpatient medication and inpatient for community-acquired pneumonia.

> It may be combined with ceftriaxone or cefuroxime for community-acquired pneumonia.

> Increasing resistance in Streptococcus pneumoniae is a problem.

> It is also useful for otitis media, sinusitis, and as single 1-g dose for nongonoccocal urethritis.

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