ISONIAZID TABLET 100mg

Isoniazid

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

4-pyridinecarbohydrazide | INH | Isoniazid | Isonicotinic acid hydrazide | Isonicotinic hydrazide | Isonicotinohydrazide | Isonicotinoylhydrazide | Isonicotinsaeurehydrazid | Isonicotinylhydrazine | Pyridine-4-carboxylic acid hydrazide | Isoniazid |

Description

Antibacterial agent used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis. [PubChem]

Indication

For the treatment of all forms of tuberculosis in which organisms are susceptible.

Mechanism of Action

Isoniazid is a prodrug and must be activated by bacterial catalase. Specficially, activation is associated with reduction of the mycobacterial ferric KatG catalase-peroxidase by hydrazine and reaction with oxygen to form an oxyferrous enzyme complex. Once activated, isoniazid inhibits the synthesis of mycoloic acids, an essential component of the bacterial cell wall. At therapeutic levels isoniazid is bacteriocidal against actively growing intracellular and extracellular Mycobacterium tuberculosis organisms. Specifically isoniazid inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis, by forming a covalent adduct with the NAD cofactor. It is the INH-NAD adduct that acts as a slow, tight-binding competitive inhibitor of InhA.

Pharmacodynamics

Isoniazid is a bactericidal agent active against organisms of the genus Mycobacterium, specifically M. tuberculosis, M. bovis and M. kansasii. It is a highly specific agent, ineffective against other microorganisms. Isoniazid is bactericidal to rapidly-dividing mycobacteria, but is bacteriostatic if the mycobacterium is slow-growing.

Pharmacokinetics

Absorption:

Readily absorbed following oral administration; however, may undergo significant first pass metabolism. Absorption and bioavailability are reduced when isoniazid is administered with food.

Distribution:

Not Available

Metabolism:

Primarily hepatic. Isoniazid is acetylated by N -acetyl transferase to N -acetylisoniazid; it is then biotransformed to isonicotinic acid and monoacetylhydrazine. Monoacetylhydrazine is associated with hepatotoxicity via formation of a reactive intermediate metabolite when N-hydroxylated by the cytochrome P450 mixed oxidase system. The rate of acetylation is genetically determined. Slow acetylators are characterized by a relative lack of hepatic N -acetyltransferase.

Elimination:

From 50 to 70 percent of a dose of isoniazid is excreted in the urine within 24 hours.

Half-life

Fast acetylators: 0.5 to 1.6 hours. Slow acetylators: 2 to 5 hours.

Clearance

Not Available

Toxicity

LD50 100 mg/kg (Human, oral). Adverse reactions include rash, abnormal liver function tests, hepatitis, peripheral neuropathy, mild central nervous system (CNS) effects. In vivo, Isoniazid reacts with pyridoxal to form a hydrazone, and thus inhibits generation of pyridoxal phosphate. Isoniazid also combines with pyridoxal phosphate; high doses interfere with the coenzyme function of the latter.

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

ISONIAZID TABLET 100mg was registered with Health Science Authority of Singapore by ATLANTIC PHARMACEUTICAL (S) PTE LTD. It is marketed with the registration number of SIN01302P with effective from 1988-05-19.

This product contains 100mg of Isoniazid in the form of TABLET.

The medicine was manufactured by ATLANTIC LABORATORIES CORPN LTD in THAILAND

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Anatomical Therapeutic Chemical (ATC) Classification

ATC Code: J04AC01

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