isoniazid

CLINICAL USE

Antibacterial agent:Treatment and prophylaxis of tuberculosis in ‘at risk’ immunocompromised patients

DOSE IN NORMAL RENAL FUNCTION

IM/IV: 200–300 mg daily Oral: 5 mg/kg to a maximum of 300 mg in single or divided dosesIntermittent regimes: 15 mg/kg twice weekly or 10 mg 3 times weeklyProphylaxis: 100–200 mg daily Intrapleural: 50–250 mg Intrathecal: 25–50 mg daily

PHARMACOKINETICS

Molecular weight :137.1

%Protein binding :0

%Excreted unchanged in urine : 4–32

Volume of distribution (L/kg) :0.75

half-life – normal/ESRD (hrs) :1.2–3.5/1–17 (depends on acetylator status)

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function

10 to 20 : Dose as in normal renal function

<10 : 200–300 mg daily

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Dialysed. Dose as in GFR

<10 : mL/min

HD :Dialysed. Dose as in GFR

<10 : mL/min

HDF/high flux :Dialysed. Dose as in GFR

<10 : mL/min

CAV/VVHD :Probably dialysed. Dose as in normal renal function

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Anti-epileptics: metabolism of carbamazepine, ethosuximide and phenytoin inhibited (enhanced effect); also with carbamazepine, isoniazid hepatotoxicity possibly increased

ADMINISTRATION

Reconstition

Dilute with water for injection if required

Route

Oral, IM, IV, intrapleural, intrathecal

Rate of Administration

Not critical. Give by slow IV bolus

Comments

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OTHER INFORMATION

Adjust dose accordingly if hepatic illness, slow/fast acetylator status identifiedPyridoxine 10 mg daily has been recommended for prophylaxis of peripheral neuritis

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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