Drug Name
Drug Action
Isoniazid (also called isonicotinyl hydrazine or INH) is a firstline antituberculous medication used in the prevention and treatment of tuberculosis.. tuberculosis Isoniazid is never used on its own to treat active tuberculosis because resistance quickly develops.
Isoniazid is active against M tuberculosis, M bovis and some strains of M kansasii. kansasii. One of its main mechanisms appears to be mycolic acid synthesis inhibition resulting in loss of acid-fastness and bacterial cell wall disruption.
Indication and Dosage
Oral PRIMARY TREATME NT OF PULMON ARY AND EXTRAPU LMONAR Y TB Adult: Daily regimen: 300 mg daily. Intermittent multipledrug regimen: 10 mg/kg 3 times/wk or 15 mg/kg twice/wk. Child: Daily regimen: 5 mg/kg daily. Max dose: 300 mg daily. Intermittent multipledrug regimen: 20-30 mg/kg (max 900 mg) twice/wk. PROPHYL AXIS OF TB Adult: 300 mg daily for at least
Adverse Reaction CNS: peripheral neuropathy, seizures, toxic encephalopathy, memory impairment, toxic psychosis. EENT: optic neuritis and atrophy. GI: nausea, vomiting, epigastric distress. Hematologic: agranulocytosis, hemolytic anemia, aplastic anemia, eosinophilia, thrombocytopenia, sideroblastic anemia. Hepatic: hepatitis, jaundice , bilirubinemia. Metabolic: hyperglycemia, metabolic acidosis, hypocalcemia, hypophosphatemia. Skin: irritation at I.M. injection site. Other: rheumatic and
lupuslike syndromes, hypersensitivity hypersensitivity reactions, pyridoxine deficiency, gynecomastia
Pharmacokinetics
Absorption: Rapid and complete; rate can be slowed with food
Pharmacodyna
Isoniazid is a prodrug and must be activ by bacterial catalase.[1] catalase.[1] It activated by Distribution: catalaseAll body tissues peroxidase and fluids enzyme KatG including CSF; form isonicot crosses acyl anion or placenta; enters radical. Thes breast milk forms will th react with a Protein binding: NADH radic 10% to 15% anion to form isonicotinic a Metabolism: NADH comp Hepatic with This complex decay rate will bind tigh determined to genetically by ketoenoylred acetylation se known as phenotype InhA and Half-life prevents acce elimination: of the natural Fast enoyl-AcpM acetylators: 30- substrate. Thi 100 minutes; mechanism Slow inhibits the acetylators: 2-5 synthesis of hours; may be mycolic acid prolonged with the hepatic or mycobacteria severe renal cell wall. impairment Isoniazid rea Time to peak, therapeutic serum: 1-2 concentration hours serum, cerebrospinal Excretion: fluid (CSF), a Urine (75% to within caseou 95%); feces; granulomas. saliva Isoniazid is
6 mth. Alternativel y, give with rifampicin for 3 mth. Child: 510 mg/kg daily. Max dose: 300 mg daily. Intramusc ular PRIMARY TREATME NT OF PULMON ARY AND EXTRAPU LMONAR Y TB Adult: Daily regimen: 300 mg daily. Intermittent multipledrug regimen: 10 mg/kg 3 times/wk or 15 mg/kg twice/wk. Child: Daily regimen: 5 mg/kg daily. Max dose: 300 mg daily. Intermittent multipledrug regimen: 20-30 mg/kg
metabolized i the liver via acetylation.. acetylation There are tw forms of the enzyme responsible f acetylation, s that some patients metabolize th drug quicker than others. Hence, the ha life is bimoda is bimoda with peaks at hour and 3 h in the US population. T metabolites a excreted in th urine. Doses not usually h to be adjuste case of renal of renal failure.. failure
(max 900 mg) twice/wk. PROPHYL AXIS OF TB Adult: 300 mg daily in a single dose. Child: 510 mg/kg daily in a single dose. Max dose: 300 mg daily.
Category C : Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.
Precaution Renal or hepatic impairment; convulsive disorders; history of psychosis; patients at risk of neuropathy or pyridoxine deficiency eg, diabetic, alcoholic, malnourished, uraemic, infected with HIV. HIV. Careful monitoring of hepatic function is necessary n ecessary for black and hispanic women. Check hepatic function before and during treatment. Pregnancy and lactation.
