AZITHROMYCIN

INTRODUCTION:

• Has extended spectrum, improved pharmacokinetics, better tolerability & drug interaction profiles.
• More active against H. influenza than other macrolides but less active against gram-positive cocci.
• High activity is exerted on respiratory pathogens-
  • Mycoplasma, Chlamydia pneumoniae, Legionella, Moraxella, Campylobacter, Ch. trachomatis, H. ducreyi, Calymm, granulomatis, N. gonorrhoea.
• However, inactive against erythromycin resistant bacteria. 

PHARMACOKINETICS:

• Acid-stability, rapid oral absorption, marked tissue distribution & intracellular penetration. 
• Mass treatment with azithromycin is indicated if the prevalence of trachoma follicles (TE) in 1-9 years population is more than 10%.
• High concentrations attained inside macrophages & fibroblasts.
• Volume of distribution is -30 L/kg.
• Long terminal t1/2 of >50 hr.
• Excreted unchanged in bile.
• Renal excretion is <10%.
• Not an enzyme inhibitor.

MECHANISM OF ACTION:

• Binds irreversibly to 50S subunit of bacterial ribosome —> Inhibiting translocation steps of protein synthesis.
  • Also, interfering with transpeptidation.
• Binding site is either identical or close proximity with clindamycin & chloramphenicol.

USES:

• First choice drug for:
• Legionnaires’ pneumonia
  • • (Development of pneumonia & diarrhoea within 10 days after hospital discharge hints to a possible diagnosis of Legionnaire’s disease.)
• rethral mucoid discharge after sexual contact with sex-worker.

Other:

• Pharyngitis
• Tonsillitis
• Sinusitis
• Otitis media
• Pneumonia
• Acute exacerbations of chronic bronchitis
• Streptococcal & some staphylococcal skin and soft tissue infections
• Typhoid
• Toxoplasmosis 
• Malaria
• Prophylaxis and treatment of MAC in AIDS patients

ADVERSE EFFECT:

• Mild gastric upset
• Abdominal pain (less than erythromycin)
• Headache 
• Dizziness

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