Essential First-Line Antituberculosis Drugs

Essential First-Line Antituberculosis Drugs

Question. Write short note on fist-line antitubercular drugs.

Answer. The first­line antitubercular drugs are Isoniazid, Rifampin, Pyrazinamide, Ethambutol and Streptomycin.

These drugs have high antitubercular efficy as well as low toxicity and are used routinely.

“Factors influencing success with first-line antituberculosis drug knowledge: Q&A”

Isoniazid

1. Isoniazid is a fist line antitubercular drug.

1. It acts on extracellular as well as intracellular TB and is equally effctive in alkaline and acidic medium.
2. The most possible action of isoniazid is inhibition of synthesis of mycolic acids which are unique fatt acid component of mycobacterial cell wall. The lipid content of Mycobacterium exposed to isoniazid is reduced.
3. Isoniazid is completely absorbed orally and penetrates all body tissues, tubercular cavities and placenta.
4. It is extensively metabolized in liver by acetylation.
5. The metabolites are excreted in urine.

“Understanding first-line antituberculosis drugs through FAQs: Mechanisms and uses explained”

Rifampin

1. Rifampin is bactericidal to M. tuberculosis.
2. Bactericidal action covers all subpopulations of TB bacilli,but acts best on slowly or intermittntly dividing ones, as well as on many atypical mycobacteria.
3. It has good sterilizing and resistance preventing actions.
   Rifampin inhibits DNA dependent RNA synthesis.
4. It is well­absorbed orally, widely distributed in the body: penetrates cavities, caseous masses, placenta and meninges.
5. It is metabolized in liver to an active deacetylated metabolite which is excreted mainly in bile, some in urine also.

“Importance of studying first-line antituberculosis drugs for healthcare professionals: Questions explained”

Pyrazinamide

1. It is weakly tuberculocidal but more active in acidic medium.
2. It is more lethal to intracellularly located bacilli and to those at sites showing an inflmmatory response (pH is acidic at both these locations).
3. It is highly effctive during the fist 2 months of therapy when inflmmatory changes are present.
4. By killing the residual intracellular bacilli, it has good ‘sterilizing’ activity.
5. It inhibits mycolic acid synthesis, but by interacting with a diffrent fatt acid synthase encoding gene.
6. Pyrazinamide is absorbed orally, widely distributed, has good penetration in CSF, extensively metabolized in liver and excreted in urine.

Ethambutol

1. Ethambutol is selectively tuberculostatic and clinically as active as S. Fast multiplying bacilli are more susceptible as are many atypical mycobacteria.
2. Ethambutol inhibits arabinosyl transferases involved in arabinogalactan synthesis and to interfere with mycolic acid incorporation in mycobacterial cell wall.
3. Patient acceptability of ethambutol is very good and side effcts are few.

“Common challenges in using first-line antituberculosis drugs effectively: FAQs provided”

Streptomycin

1. It was the fist clinically useful antitubercular drug.
2. It is tuberculocidal, but less effective than rifampin;acts only on extracellular bacilli. Thus, host defense mechanisms are needed to eradicate the disease.
3. It penetrates tubercular cavities, but does not cross to the CSF, and has poor action in acidic medium.
4. Resistance developed rapidly when streptomycin was used alone in tuberculosis–most patients had a relapse.