Drugs Use In Tuberculosis - ANTIMMYCOBACTERIALS (From lipincott Review for screening test)

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 Mycobacteria

 rod shaped, lipid-rich cell wall, satin poorly with Gram stain, but once stained , walls cannot decolorized easily so called “Acid-Fast”.

Most common bacteria Tuberculosis…Diagnosed by Tuberclin-Skin test with PPD (Purified protein derivative) or by IGRA (interferon Gamma Releas essay), Quntiferon-TB Gold. 

Chemotherapy for Tuberculosis

Mycobacteria tuberculosis caused Tuberculosis i.e infection of lungs, genitourinary tract,Skeleton, Meninges.

👉 Organism grow slowly, difficult to culture, take 6month to 2yr for treatment.

Stratgies to address Drug Resistance: 

combination of “First-line” initial short-course for 2month with Isoniazid,Rifampicin, Ethambutol, Pyrazinamide…… then “continuation phase” Isoniazid & Rifampicin for 4 months.

DOT progaramme “Directly Observed Therapy” pt. observed when take medicine to↓resistance.



Isoniazid (Bacteriostatic /Bactericidal)

Hydrozyde of Isonicotinic acid...synthetic analogue of Pyridoxine…

MOA:

 Prodrug catalyzed by KatG (Mycobacterial catalase-peroxidase)….Active form….ϴ InHA (enoyl-acyl carrier protein reductase) & KaSA (β-ketoacyl-ACP synthase)….ϴMycolic acid (β-OH,produced by Typell fats)…loss of Fastness..destruction of cell wall

Antibacterial spectrum:

active against M.tuberculosis, M.kansasii

Resistance

mutation or deletion of KatG…

P.K

orally..food ↓ abs..CSF level high..undergo N-acetylation produce Fast acetylator dominant trait…Fast & slow acetylator…Slow acetyltor excrete more parent compound ..

S.E

Peripheral neuritis (Paresthesia of feet, hand) due to deficiency of VitB6(Pyridoxine).. Hepatitis by MonoacetylHydrazine… Enzyme inhibitor

Rifamycin:

 Rifampin Rifabutin, Rifapentine

Rifampin (Bactericidal) :

 derived from Streptomyces…Broader anti-microbial activity…

MOA:

 block transcription by interacting β-subunit of bacterial DNA-dependent RNA polymerase…ϴ mRNA synthesis

Antimicrobial spectrum

have activity for M.tuberculosis, M.kansasii, M.leprsoy, M-avium used in Meningitis by H.influenza,

S.E:

Hepatitis Flu-like syndrome….Urine, feces & tears have orange-red color…Enzyme inducer.

Rifabutin:

used in HIV patients with Tuberculosis…cause Uveitis, hyperpigmentation,neutropenia

Pyrazinamide (Bactericidal)

Unknown mechanism...Hydrolyze into” Pyrazinoic acid” active form…

S.E

Gout↑uric acid

Ethambutol (Bacteriostatic)

ϴBinocyl transferase…an enzyme required for Arabinogalactan cell wall…

S.E; Optic neuritis (inability to discriminate Red & Green)

Second-line agent

Streptomycin:

First antibiotic in Tuberculosis

Capreomycin

pepetide ϴ protein synthesis...for multidrug resistant tuberculosis

Cycloserine

Tuberculostatic agent…ϴ D-alanine in cell wall synthesis...cause peripheral neuropathy

Ethionamide

 analogue of Isoniazid…ϴacetylation of Isoniazid.

Chemotherapy for LEPROSY

Leprosy= (Hansen‟s disease) bacilli from skin or nasal discharge enter into skin or respiratory sys of patient….

Dapsone (Bacteriostatic) 

ϴFolate synthesis…activity for M.leprsoy, P.jivoreci cause Penumonia in HIV pt….

S.E

hemoglobinemia, peripheral neuropathy, Erythema nodosum

Clofazimine (Bactericidal) 

 Phenazine dye bind to DNA & ϴ DNA replication...Redox property produces toxic O2…

S.E

Red-Brown discoloration, eiosinophilic enteritis (anti-inflammatory properties). 


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