CLINICAL USE

Anti-epileptic agent

DOSE IN NORMAL RENAL FUNCTION

15–45 mg daily in 3 divided doses if dose >30 mg

PHARMACOKINETICS

  • Molecular weight                           : 412
  • %Protein binding                           : 96
  • %Excreted unchanged in urine     : <2
  • Volume of distribution (L/kg)       : 1
  • half-life – normal/ESRD (hrs)      : 7–9 (2–3 in patients on enzyme inducing drugs)

    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           : Dose as in normal renal function

    DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

  • CAPD                : Unknown dialysability. Dose as in normal renal function
  • HD                     : Not dialysed. Dose as in normal renal function
  • HDF/high flux   : Unknown dialysability. Dose as in normal renal function
  • CAV/VVHD      : Unknown dialysability. Dose as in normal renal function

    IMPORTANT DRUG INTERACTIONS

    Potentially hazardous interactions with other drugs

  • Antidepressants: antagonism of anticonvulsant effect (convulsive threshold lowered)
  • Anti-epileptics: concentration reduced by phenytoin, carbamazepine, phenobarbital and primidone
  • Antimalarials: mefloquine antagonises anticonvulsant effect; chloroquine and hydroxychloroquine occasionally reduce convulsive threshold

    ADMINISTRATION

    Reconstition

    Route

    Oral

    Rate of Administration

    Comments

    OTHER INFORMATION

    Although there is no evidence of withdrawal seizures, it is recommended to taper off treatment over a period of 2–3 weeks .

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