The kidneys play a pivotal role in processing allopurinol. Approximately 80% of allopurinol is excreted unchanged in urine, highlighting the kidney’s primary function in eliminating this medication.
Renal function directly impacts allopurinol clearance. Reduced kidney function slows elimination, leading to higher allopurinol blood levels. This increased concentration raises the risk of side effects, primarily related to the allopurinol metabolite, oxypurinol.
Oxypurinol, unlike allopurinol, primarily undergoes renal excretion. Its longer half-life means that elevated blood levels persist longer in patients with impaired kidney function.
Therefore, careful monitoring of renal function, through measures like serum creatinine and estimated glomerular filtration rate (eGFR), is crucial before initiating allopurinol therapy and during treatment. Dosage adjustments are often necessary for patients with reduced kidney function to prevent adverse events.
| Normal | Standard dose |
| Mildly Impaired (eGFR 50-80 mL/min/1.73m²) | May require dose reduction |
| Moderately Impaired (eGFR 30-49 mL/min/1.73m²) | Significant dose reduction often needed |
| Severely Impaired (eGFR | Dose reduction or alternative treatment may be necessary |
Regular blood tests to monitor allopurinol and oxypurinol levels can further guide dose adjustments and ensure safe and effective treatment.
