AZITHROMYCIN

INTRODUCTION:
  • Has an expanded spectrum, improved pharmacokinetics, better tolerability and drug interaction profiles.
  • It is more active than other macrolides against H. influenzae, but less active against gram-positive cocci.
  • High activity is exerted on respiratory pathogens-
  • > Mycoplasma,Chlamydia pneumoniae, Legionella, Moraxella and on others like Campylobacter, Ch. trachomatis, H. ducreyi, Calymm, granulomatis, N. gonorrhoeae.
  • However, it is not active against erythromycin resistant bacteria. Good activity is noted against MA
PHARMACOKINETICS:
  • Acid-stability, rapid oral absorption, marked tissue distribution and intracellular penetration. 
  • Mass treatment with azithromycin is indicated if prevalence of trachoma follicles (TE) in 1-9 years population is more than 10% 
  • High concentrations are attained inside macrophages and fibroblasts; volume of distribution is -30 L/kg.
  • Long terminal t1/2 of >50 hr.
  • Excreted unchanged in bile, renal excretion is - 10%.
MECHANSIM OF ACTION:
  • The macrolides bind irreversibly to a site on the 50S subunit of the bacterial ribosome, thus inhibiting the translocation steps of protein synthesis .
  • They may also interfere at other steps, such as transpeptidation. Their binding site is either identical or in close proximity to that for clindamycin and chloramphenicol.
USES:
  1. First choice drug for infections such as:
  2. Legionnaires' pneumonia(Development of pneumonia and diarrhea within 10 days after discharge from hospital hints to a possible diagnosis of Legionnaire's disease.)
  3. Chlamydia trachomatis
  4. Donovanosis caused by Calymmatobacterium Granulomatis
  5. Chancroid and PPNG urethritis(urethral mucoid discharge after sexual contact with a sex-worker)
  • Other:
  1. Pharyngitis
  2. Tonsillitis, 
  3. Sinusitis, 
  4. Otitis media, 
  5. Pneumonias, 
  6. Acute exacerbations of chronic bronchitis, 
  7. Streptococcal and some staphylococcal skin and soft tissue infections
  8. Typhoid, 
  9. Toxoplasmosis 
  10. Malaria
  11. Prophylaxis and treatment of MAC in AIDS patients
ADVERSE EFFECT:
  • Mild gastric upset, 
  • Abdominal pain (less than erythromycin), 
  • Headache 
  • Dizziness.
Exam Question
  • A patient with discharge per vagina was evalu­ated and on endocervical biopsy Chlamydia was found. Treatment to be given in this case is Azithromycin and contact tracing A young boy presented with high fever shows clinical features suggestive of Legionnaires' Disease. Treatment of choice is Azithromycin 
  • The drug of choice to treat Chlamydia infection in pregnancy is Azithromycin 
  • Mass treatment with azithromycin is indicated if prevalence of trachoma follicles (TE) in 1-9 years population is more than 10%
  • A 30 year old male presents with pneumonia and diarrhea five days after discharge from a hospital. The drug of choice for treating him is Azithromycin
  • 24 years old male complains of mild urethral mucoid discharge after sexual contact with a sex-worker. Examination is normal. Drug used to treat such a patient is Azithromycin Treatment of graunolma inguinale is Azithromycin

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