Allopurinol

CLINICAL USE

  • Gout prophylaxis
  • Hyperuricaemia

    DOSE IN NORMAL RENAL FUNCTION

    100–900 mg/day (usually 300 mg/day)
    Doses above 300 mg should be given in
    divided doses

    PHARMACOKINETICS

  • Molecular weight                           :
    136.1
  • %Protein binding                           :
    <5
  • %Excreted unchanged in urine     :
  • <10           :
  • Volume of distribution (L/kg)       :
    1.6
  • half-life – normal/ESRD (hrs)      :
    1–2/Increased

    DOSE IN RENAL IMPAIRMENT

    GFR (mL/MIN)

  • 20 to 50     : 200–300 mg daily
  • 10 to 20     : 100–200 mg daily
  • <10           :
    100 mg daily or 100 mg on alternate
    days

    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      :
    Dialysed. Dose as in GFR=10–
    20 mL/min

    IMPORTANT DRUG INTERACTIONS

    Potentially hazardous interactions with other drugs

  • ACE inhibitors: increased risk of toxicitywith captopril
  • Ciclosporin: isolated reports of raisedciclosporin levels (risk of nephrotoxicity)
  • Cytotoxics: effects of azathioprine andmercaptopurine enhanced with increased
    toxicity; avoid concomitant use with
    capecitabine

    ADMINISTRATION

    Reconstition

    –

    Route

    Oral

    Rate of Administration

    –

    Comments

  • In all grades of renal impairmentcommence with 100 mg/day and increase
    if serum and/or urinary urate response is
    unsatisfactory. Doses less than 100 mg/day
    may be required in some patients
  • Take as a single daily dose, preferably afterfood

    OTHER INFORMATION

    A parenteral preparation is available from

    Glaxo Wellcome on a named patient basis

  • HD patients may be given 300 mg postdialysis, i.e. on alternate days
  • Increased incidence of skin rash inpatients with renal impairment
  • Efficient dialysis usually controls serumuric acid levels
    If a patient is prescribed azathioprine or

    6-mercaptopurine concomitantly, reduce
    azathioprine or 6-mercaptopurine dose by
    66–75%

  • Main active metabolite: oxipurinol –renally excreted; plasma protein binding
    17%; half-life: Normal/ESRF = 13–
    30/>125 hours – 1 week
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