Isoniazid
From Wikipedia, the free encyclopedia
| Image:Izoniazid.png | |
| Isoniazid
| |
| Systematic (IUPAC) name | |
| pyridine-4-carbohydrazide | |
| Identifiers | |
| CAS number | 54-85-3 |
| ATC code | J04AC01 |
| PubChem | 3767 |
| DrugBank | APRD01055 |
| Chemical data | |
| Formula | C6H7N3O |
| Mol. weight | 137.139 g/mol |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Protein binding | Very low (0-10%) |
| Metabolism | liver; CYP450: 2C19, 3A4 inhibitor |
| Half life | 0.5-1.6h (fast acetylators), 2-5h (slow acetylators) |
| Excretion | urine (primarily), feces |
| Therapeutic considerations | |
| Pregnancy cat. |
C |
| Legal status |
prescription only (US) |
| Routes | oral, intramuscular, intravenous |
Isoniazid (also called isonicotinyl hydrazine or isonicotinic acid hydrazide) is often abbreviated INH. Isoniazid is a first-line antituberculous medication used in the prevention and treatment of tuberculosis.
It is available in tablet, syrup, and injectable forms (given intramuscularly or intravenously), available world-wide, inexpensive to produce and is generally well tolerated.
Contents |
[edit] Mechanism of action
Isoniazid is a prodrug and must be activated by bacterial catalase. The active form inhibits the synthesis of mycolic acid in the mycobacterial cell wall.
Isoniazid reaches therapeutic concentrations in serum, cerebrospinal fluid (CSF), and within caseous granulomas. Isoniazid is metabolized in the liver via acetylation. There are two forms of the enzyme responsible for acetylation, so that some patients metabolize the drug quicker than others. Hence, the half-life is bimodal with peaks at 1 hour and 3 hours in the US population. The metabolites are excreted in the urine. Doses do not usually have to be adjusted in case of renal failure.
Isoniazid is bactericidal to rapidly-dividing mycobacteria, but is bacteriostatic if the mycobacterium is slow-growing.
[edit] Side effects
Adverse reactions include rash, abnormal liver function tests, hepatitis, sideroblastic anemia, peripheral neuropathy, mild central nervous system (CNS) effects, and drug interactions resulting in increased phenytoin (Dilantin) or disulfiram (Antabuse) levels.
Peripheral neuropathy and CNS effects are associated with the use of isoniazid and are due to pyridoxine (vitamin B6) depletion, but are uncommon at doses of 5 mg/kg. Persons with conditions in which neuropathy is common (e.g., diabetes, uremia, alcoholism, malnutrition, HIV-infection), as well as pregnant women and persons with a seizure disorder, may be given pyridoxine (vitamin B6) (10-50 mg/day) with isoniazid.
INH therapy will also decrease the efficacy of hormonal birth control.
[edit] Wikipedia links
[edit] References
- Core Curriculum on Tuberculosis (2000) Division of Tuberculosis Elimination, Centers for Disease Control and Prevention
See Chapter 6, Treatment of LTBI Regimens - Isoniazid
See Chapter 7 - Treatment of TB Disease Monitoring - Adverse Reactions to First-Line TB Drugs - Isoniazid
See Table 5 First-Line Anti-TB Medications
- Isoniazid Overdose: Recognition and Management American Family Physician 1998 Feb 15
es:Isoniacida fr:Isoniazide pl:Izoniazyd nl:Isoniazide nn:Isoniazid
