Anti Tuberculosis drugs.

Isoniazid(INH)

  • Inhibits mycolic acid cellwall synthesis¬† via oxygen dependent pathways.
  • Bactericidal to both extracellular and intracellular organism
  • SE:Peripheral neuritis,seizures,hepatitis,optic neuritis,hemolysis in G6PD deficiency,SLE like syndrome.
  • Pyridoxine 10mg orally given as prophylaxis for optic neuritis.
  • INH-Is Hepatotoxic and Neurotoxic.

Rifampicin

  • Blocks RNA synthesis by blocking DNA dependent RNA polymerase.
  • Bactericdal, acts best on intermittently dividing organisms(spurters)
  • Hepatotoxic,enzyme inducer(P450)
  • Orange colored urine and sweat.

Pyrazinamide

  • Inhibits mycolic acid synthesis.
  • Bactericidal to slowly dividing intracellular bacilli and those within caseous granuloma.
  • More active at PH<6,god penetration into CNS.
  • Hepatotoxic, hyperuricemia.

Ethambutol

  • Inhibits arabinosyl transferases and interferes with mycolic acid incorporation into bacterial cell wall.
  • Bacteriostatic, acts on fast dividing bacilli and atypical mycobacteria,least potent anti TB drug.
  • Optic neuritis and Redgreen color vision disturbance.
  • Ethambutol affect Eye.

Streptomycin

  • Bind to 30S ribosomal subunit freeze initiation of protein synthesis and cause misreading of mRNA code.
  • Bactericidal to extra cellular bacilli
  • Ototoxic and nephrotoxic.

Importan Points: Most of these drugs are hepatotoxic except Streptomycin and Ethambutol.

INH resistance is associated with decreased catalase and peroxidase activity in the bacteria.

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