Product Information

Registration Status: Active

ISONIAZID TABLET 100mg is approved to be sold in Singapore with effective from 1988-05-19. It is marketed by ATLANTIC PHARMACEUTICAL (S) PTE LTD, with the registration number of SIN01302P.

This product contains Isoniazid 100mg in the form of TABLET. It is approved for ORAL use.

This product is manufactured by ATLANTIC LABORATORIES CORPN LTD in THAILAND.

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



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


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.


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


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.

Active Ingredient/Synonyms

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


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