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

    –

    OTHER INFORMATION

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

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