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Oral formulations of allopurinol.

Drugs List

  • allopurinol 100mg tablets
  • allopurinol 300mg tablets
  • URICTO 300mg tablets
  • ZYLORIC 100mg tablets
  • ZYLORIC 300mg tablets
  • Therapeutic Indications


    Gout (prophylaxis)
    Prophylaxis against recurrent renal calcium stones

    Reduction of urate/uric acid formation in conditions where urate/uric acid deposition has occurred (e.g. gouty arthritis, skin tophi, nephrolithiasis) or is a risk (e.g. treatment of malignancy which could result in acute uric acid nephropathy, or enzyme disorders leading to excess urate e.g. Lesch-Nyhan syndrome).

    Management of 2,8-dihydroxyadenine (2,8-DHA) renal stones related to deficient activity of adenine phosphoribosyltransferase.

    Management of recurrent mixed calcium oxalate renal stones in the presence of hyperuricosuria, when fluid, dietary and other measures have failed.



    Initial dose 100mg daily increasing only if serum urate does not decrease to desirable level.

    Mild conditions: 100mg to 200mg daily.

    Moderately severe conditions: 300mg to 600mg daily.

    Severe conditions: 700mg to 900mg daily.

    If dose is calculated on a mg/kg bodyweight basis, a dose of 2mg/kg to 10mg/kg daily should be used.


    Rarely indicated in children except in malignant conditions (in particular leukaemia) and certain enzyme disorders such as Lesch-Nyhan syndrome.
    Children aged 15 to 18 years: (See Dosage; Adults).

    Children aged 1 month to 15 years: 10mg/kg to 20mg/kg daily (up to a maximum of 400mg daily).

    Patients with Renal Impairment

    Severe renal impairment: Consider daily dose of less than 100mg, or single doses of 100mg at intervals of longer than one day.

    Adjust dose to maintain plasma oxipurinol concentrations below 100micromol/l (15.2mg/l) if possible.

    Allopurinol and its metabolites are removed by renal dialysis. If dialysis is required two to three times a week, consider giving 300mg to 400mg of allopurinol immediately after each dialysis with no doses in between.

    Additional Dosage Information

    If the daily dose exceeds 300mg and gastrointestinal intolerance occurs, consider divided doses.

    Treatment of high urate turnover conditions e.g. neoplasia, Lesch-Nyhan syndrome
    Existing hyperuricaemia and/or hyperuricosuria should be corrected with allopurinol before starting cytotoxic therapy. Ensure adequate hydration to maintain optimum diuresis and attempt alkalisation of the urine to increase solubility of urinary urate/uric acid. The dose of allopurinol should be at the lower end of the recommended regimen.



    Precautions and Warnings

    Glucose-galactose malabsorption syndrome
    Hepatic impairment
    Lactose intolerance
    Renal impairment
    Thyroid dysfunction

    Do not initiate during an acute attack of gout
    Reduce dose in patients with hepatic impairment
    Reduce dose in patients with renal impairment
    Administer anti-inflammatory in first month:Reduces risk of gouty arthritis
    Confirm HLA-B 5801 status in Han Chinese, Thai and Korean patients
    Contains lactose
    Advise patient to avoid aluminium hydroxide 3 hours before or after dose
    Ensure patient has adequate fluid intake
    Never rechallenge treatment after a severe hypersensitivity reaction
    Advise patient to seek medical advice if severe skin reaction occurs
    Discontinue if hypersensitivity reactions occur
    Discontinue treatment if skin rash or other allergic reaction occurs

    In conditions where the rate of urate formation is greatly increased (e.g. malignancy), the absolute concentration of xanthine in the urine could rise sufficiently to allow deposition in the urinary tract. This risk may be minimised by adequate hydration to achieve optimal urine dilution.

    Adequate therapy with allopurinol will lead to dissolution of large uric acid renal pelvic stones, with the remote possibility of impaction in the ureter.

    Hypersensitivity syndrome, Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported during allopurinol treatment. Carriers of the HLA-B*5801 allele appear to be at an increased risk, particularly those of Han Chinese, Thai or Korean descent. Pre-treatment screening for the allele is recommended in patient subgroups where this genotype has a high prevalence. Patients identified as carriers of the allele should not initiate treatment unless there is no alternative therapeutic option and benefits outweigh potential risks. If used, monitor closely for signs of hypersensitivity and inform patients to stop treatment immediately at the first appearance of any symptoms. Where genotyping is unavailable, decision to initiate treatment should be made on a risk benefit basis. It should be noted, SJS/TEN can also occur in patients negative for HLA-B*5801, irrespective of their ethnic origin.

    Pregnancy and Lactation


    Use allopurinol with caution during pregnancy.
    Manufacturers advise that although allopurinol has been widely used during pregnancy without apparent harm, there is insufficient evidence of safety and it should only be used if there is no safer alternative and the condition itself poses a risk to the mother and baby.
    Animal studies have shown conflicting results regarding foetal abnormalities.


    Use allopurinol with caution during breastfeeding.
    Manufacturers state that allopurinol is not recommended during breastfeeding.
    Allopurinol and its metabolite oxipurinol are excreted in human breast milk, however the effect on the infant is unknown.

    Side Effects

    Altered bowel habit
    Altered liver function tests
    Angioimmunoblastic lymphadenopathy
    Aplastic anaemia
    Diabetes mellitus
    Discolouration of hair
    Drug rash with eosinophilia and systemic symptoms (DRESS)
    Erectile dysfunction
    Exfoliative rash
    Fixed drug eruption
    Granulomatous hepatitis
    Hepatic impairment
    Hepatic necrosis
    Hypersensitivity reactions
    Macular abnormalities
    Maculopapular rash
    Male infertility
    Pruritic rash
    Renal impairment
    Stevens-Johnson syndrome
    Taste disturbances
    Toxic epidermal necrolysis
    Visual disturbances


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: May 2019

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

    Summary of Product Characteristics: Uricto 100mg tablets. Ennogen Ltd. Revised January 2018.
    Summary of Product Characteristics: Uricto 300mg tablets. Ennogen Ltd. Revised January 2018.

    Summary of Product Characteristics: Zyloric tablets 100mg. Aspen. Revised February 2019.
    Summary of Product Characteristics: Zyloric tablets 300mg. Aspen. Revised February 2019.

    NICE Evidence Services Available at: Last accessed: 10 May 2019

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    FDB Disclaimer : FDB Multilex is intended for the use of healthcare professionals and is provided on the basis that the healthcare professionals will retain FULL and SOLE responsibility for deciding what treatment to prescribe or dispense for any particular patient or circumstance.