Antitubercular Agents : Reserve drugs

Antitubercular Agents - Synthesis and Drug Profile

Reserve drugs

i. Ethionamide (Tridocin)

Synthesis

Route I. From: 2-Ethyl-4-cyanopyridine

Route II. From: Ethyl propionyl pyruvate

Mode of action: The antimycobacterial action of ethionamide seems to be due to an inhibitory effect on the mycolic acid synthesis.

Metabolism: Less than 1% of the drug is excreted in the free form, and remainder of the drug appear as six metabolites. Among the metabolites, ethionamide sulphoxide, 2-ethyl-isonicotinamide, and the N-methylated-6-oxo-dihydropyridines are the few.

Properties and uses: Ethionamide is a yellow crystalline powder or crystals, practically insoluble in water, soluble in methanol, and sparingly soluble in alcohol. It is used as antitubercular drug.

Assay: Dissolve the sample in anhydrous acetic acid and titrate with 0.1 M perchloric. Determine the end point potentiometrically.

Dose: The dose to be administered is 500 mg–1 g per day in three or four divided doses with meals.

ii. Para-amino-salicylic acid (PAS, Tubacin)

Mode of action: Aminosalicylic acid is an inhibitor of bacterial folate metabolism in a manner similar to the sulphonamide antibacterials.

Properties and uses: Aminosalicylic acid is bacteriostatic and highly specific for M. tuberculosis. Side effects are anorexia, nausea, epigastric pain, diarrhoea, and making poor compliance.

Dose: Dose administered orally 14–16 g daily after meals in three to four divided doses.

Synthesis

Route I. From: Anthranilic acid

Route II. From: m-Nitrophenol

iii. Amikacin

Properties and uses: Amikacin is a white powder, soluble in water, practically insoluble in acetone and in ethanol. It is a semisynthetic aminoglycoside that was first prepared in Japan. It is extremely active against several mycobacterial species, and may become the drug of choice for treatment of diseases caused by nontuberculous mycobacteria.

Assay: It is assayed by adopting liquid chromatography technique.

Dosage forms: Amikacin sulphate injection I.P., Amikacin injection B.P.

iv. Thiacetazone

Synthesis

Uses: It is used as an antitubercular agent.