- Molecular NameIsoniazid
- SynonymHIA; Hydrazid; Hydrazide; INH; Isohydrazide; Isonicotinhydrazid; Isonicotinic acid hydrazide; Isonicotinic hydrazide; Isonicotinohydrazide; Isonicotinoyl hydrazide; Isonicotinyl hydrazide; Isonicotinyl hydrazine; Isonicotinylhydrazine
- Weight137.142
- Drugbank_IDDB00951
- ACS_NO54-85-3
- Show 3D model
- LogP (experiment)-0.64
- LogP (predicted, AB/LogP v2.0)-0.68
- pka1.8, 3.5, 10.8
- LogD (pH=7, predicted)-0.68
- Solubility (experiment)140 mg/ml
- LogS (predicted, ACD/Labs)(ph=7)0.0
- LogSw (predicted, AB/LogsW2.0)79.25
- Sw (mg/ml) (predicted, ACD/Labs)136.21
- No.of HBond Donors3
- No.of HBond Acceptors4
- No.of Rotatable Bonds1
- TPSA68.01
- StatusFDA approved
- Administrationoral, intramuscular, intravenous
- PharmacologyAn organic compound that is the first-line antituberculosis medication in prevention and treatment.
- Absorption_value80.0
- Absorption (description)Readily absorbed following oral administration; however, may undergo significant first pass metabolism. Absorption and bioavailability are reduced when isoniazid is administered with food.
- Caco_2N/A
- Bioavailability80.0
- Protein binding0.0
- Volume of distribution (VD)0.67 L/kg
- Blood/Plasma Partitioning ratio (D_blood)N/A
- Metabollsmliver; CYP450: 2C19, 3A4 inhibitor. The main metabolic reaction is acetylation and the rate at which this occurs shows genetic variation, approximately 40% of the population being rapid acetylators and the remainder slow acetylators. Other metabolic reactions which occur are hydrolysis, glycine conjugation, hydrazone formation and N-methylation. Metabolites include acetylisoniazid, isonicotinic acid, isonicotinylglycine, and mono- and diacetylhydrazine. All the metabolites are inactive with the exception of monoacetylhydrazine which is a reactive metabolite and is hepatotoxic.
- Half life1.1 h in rapid acetylators and 3.1 h in slow acetylators.
- ExcretionUp to about 70% of a dose is excreted in the urine in 24 h, most being excreted in the first 12 h. In slow acetylators, about 30% of the dose is excreted in the urine as unchanged drug, up to about 25% as acetylisoniazid, about 10% as isonicotinic acid and about 8% as diacetylhydrazine. In rapid acetylators, about 10% of a dose is excreted as unchanged drug, up to 45% as acetylisoniazid, about 20% as isonicotinic acid and about 25% as diacetylhydrazine. Small amounts of monoacetylhydrazine are also excreted in the urine. Less than 10% of a dose is eliminated in the faeces.
- Urinary Excretion7 (rapid acetylators) or 29 (slow acetylators)
- Clerance3.7 and about 7.4 ml/min/kg in slow and rapid acetylators, respectively.
- ToxicitySerious toxic symptoms may occur with doses of 3 g or more. In children, toxic effects have occurred after ingestion of 0.9 g or more but a child has recovered after taking as much as 20 g. Toxic effects have been associated with plasma concentrations greater than 20 mg/L.
- LD50 (rat)N/A
- LD50 (mouse)N/A