What do you need to check before starting a patient on allopurinol?

Pre-Allopurinol Assessment Checklist

Before starting allopurinol, you must check HLA-B*5801 status in patients of Southeast Asian descent (Han Chinese, Korean, Thai) and African American patients due to the significantly increased risk of allopurinol hypersensitivity syndrome (AHS), which can be life-threatening. 1

Essential Pre-Treatment Assessments

Genetic Testing

• HLA-B*5801 testing:
  • Required for: Southeast Asian descent (Han Chinese, Korean, Thai) and African American patients 1
  • Not routinely recommended for: White and Hispanic patients (lower prevalence of 0.7%) 1
  • Rationale: HLA-B*5801 carriers have markedly elevated risk for AHS 1

Renal Function Assessment

• Baseline renal function tests (BUN, serum creatinine, eGFR) 2, 3
  • Critical for dosing decisions as allopurinol and its metabolite oxipurinol are eliminated by kidneys 3
  • Patients with decreased renal function require lower starting doses:
    • For moderate to severe CKD: Start at ≤50 mg/day 2
    • For creatinine clearance 10-20 mL/min: Maximum 200 mg/day 2
    • For creatinine clearance <10 mL/min: Maximum 100 mg/day 2

Liver Function

• Baseline liver function tests 3
  • Particularly important in patients with pre-existing liver disease
  • Regular monitoring recommended during early stages of therapy

Baseline Serum Uric Acid

• Serum uric acid level to establish baseline and monitor treatment efficacy 2
  • Target levels: <6 mg/dL for most patients, <5 mg/dL for severe tophaceous gout 2

Medication Review

• Check for potential drug interactions with:
  • Azathioprine/mercaptopurine: Require 65-75% dose reduction 1, 3
  • Anticoagulants (especially dicumarol): Monitor prothrombin time 3
  • Thiazide diuretics: Increased risk of allopurinol toxicity 3
  • Ampicillin/amoxicillin: Increased risk of skin rash 3
  • Cyclosporine: Potential for interaction 1, 3

Prophylaxis Planning

• Anti-inflammatory prophylaxis must be prescribed concurrently to prevent gout flares 2:
  • First choice: Colchicine 0.5-1 mg daily (reduce dose in renal impairment)
  • Alternative: NSAIDs (e.g., naproxen 250 mg twice daily)
  • If contraindicated: Low-dose prednisone/prednisolone
  • Duration: Continue for 3-6 months after starting allopurinol

Patient Education Requirements

1. Hypersensitivity awareness: Instruct patients to stop medication and seek immediate medical attention if they develop skin rash, painful urination, blood in urine, eye irritation, or swelling of lips/mouth 3

2. Hydration guidance: Advise maintaining fluid intake of at least 2 liters daily to prevent kidney stones 3

3. Medication adherence: Explain that optimal benefit may be delayed for 2-6 weeks 3

4. Dosing schedule: Start at low dose (≤100 mg/day) with gradual titration 2

Common Pitfalls to Avoid

1. Starting with too high a dose, especially in renal impairment

   • Always start at ≤100 mg/day (lower in renal impairment) 2

2. Inadequate prophylaxis against acute gout flares

   • Failure to provide anti-inflammatory prophylaxis can lead to painful flares 2

3. Missing HLA-B*5801 testing in high-risk ethnic groups

   • Can lead to potentially fatal hypersensitivity reactions 1

4. Overlooking drug interactions

   • Particularly with azathioprine/mercaptopurine, which require significant dose reductions 1, 3

5. Insufficient monitoring

   • Regular monitoring of renal function, liver function, and serum uric acid is essential 2, 3

By following this comprehensive pre-treatment assessment protocol, you can significantly reduce the risk of adverse events and optimize treatment outcomes for patients starting allopurinol therapy.