Allopurinol

Related Subjects: | Hyperuricaemia | Acute and Chronic Gout | Allopurinol | Rasburicase

Take great care in starting. There is a risk of SJS or TEN (Asian HLA-B*5801 allele) and there are also several potentially lethal drug interactions with Allopurinol and Azathioprine or Mercaptopurine or Ciclosporin. Side effects are rash, pruritus, cytopenia, diarrhoea, toxic epidermolysis and Stevens-Johnson syndrome.

About : Always check the BNF link here

• Its metabolite alloxanthine is the active drug
• ****Can be lethal if given with other drugs see below****

Actions

• Blocks the conversation of xanthine to uric acid
• Xanthine oxidase inhibitor reducing uric acid production from purines

Indications/Dose: Check BNF

• Chronic gout: Allopurinol 100-300 mg od po with food. Max 900 mg/day.
  • Do not start as single agent until at least 4 weeks after acute gout.
  • Use lowest dose to keep uric acid <6 mg/dL.
• Acute Episode: An NSAID or low dose of Colchicine can be given for a month initially along with Allopurinol 100 mg to prevent acute attacks.
• Tumour lysis syndrome: Allopurinol 100-300 mg 8 h.
• This is not an innocuous drug and should not be used for asymptomatic hyperuricaemia

Dose Range

Contraindications

• Acute gout. If an attack happens on Allopurinol there is no need to stop Allopurinol.
• If starting following acute attack then combined with Colchicine or NSAID

Cautions

• Ensure adequate fluid intake.
• Reduce dose in Renal Impairment and Liver disease

Interactions

• Be careful as there is the potential for severe fatal toxicity if given with Azathioprine, Mercaptopurine or Ciclosporin. Doses will need adjusting.
• Can cause Azathioprine toxicity - LETHAL WARNING
• Can cause 6 Mercaptopurine toxicity - LETHAL WARNING
• Can affect Warfarin levels - watch INR
• Can increase levels of ACEI/AT2 antagonists
• Can increase levels of cyclophosphamide

Side effects

• Acute gout, Rash rarely Stevens-Johnson syndrome - stop the drug if rash develops
• Interstitial nephritis, Hepatitis, Eosinophilia, Gynaecomastia, Metallic taste in the mouth
• Drug Rash with Eosinophilia and Systemic Symptoms (DRESS)
• Generalized vasculitis, irreversible hepatotoxicity,

References

• Allopurinol in BNF