Plasma oxipurinol concentrations during allopurinol therapy.

Area of Science:

• Pharmacology
• Nephrology
• Rheumatology

Background:

• Allopurinol is a common treatment for gout.
• Oxipurinol is the primary active metabolite of allopurinol.
• Understanding oxipurinol pharmacokinetics is crucial for optimizing gout management.

Purpose of the Study:

• To investigate the relationship between allopurinol dosage, renal function, and plasma oxipurinol concentrations.
• To determine effective plasma oxipurinol concentration ranges for controlling hyperuricaemia.
• To assess the utility of these measurements in patients with suboptimal treatment response.

Main Methods:

• Studied 66 gout patients with varying allopurinol doses (100-400 mg/day).
• Assessed patients with normal to moderately impaired renal function.
• Correlated plasma oxipurinol levels with allopurinol dosage and plasma creatinine concentration.

Main Results:

• Plasma oxipurinol concentrations showed a direct correlation with allopurinol dosage and renal function (plasma creatinine).
• Concentrations of 30-100 mumol/l were generally effective for hyperuricaemia control.
• Higher allopurinol doses (>300 mg/day) in patients with impaired renal function (creatinine ≥0.2 mmol/l) often led to oxipurinol levels exceeding this effective range.
• In normal renal function, plasma xanthine levels of 6-9 mumol/l indicated adequate xanthine oxidase inhibition.

Conclusions:

• Plasma oxipurinol levels are influenced by allopurinol dosage and renal function.
• Therapeutic drug monitoring of oxipurinol can guide allopurinol dose adjustments.
• These measurements are valuable for optimizing treatment in patients with persistent hyperuricaemia despite standard allopurinol doses.