Gout has a strong association with the metabolic syndrome, and it is often seen in patients with renal insufficiency. Allopurinol is a medication intended to lower uric acid and therefore prevents gout attacks. Its metabolism is mainly renal, and some evidence shows that it is also dialyzable. The hypothesis is that allopurinol would be more efficacious to lower uric acid if it was given after dialysis only. The investigators will then switch administration of allopurinol to bedtime for dialysis patients currently taking that medication.

Gout has a strong association with the metabolic syndrome, and it is often seen in patients with renal insufficiency. A study has shown an incidence of fifteen percent of gout in the first five years spent in dialysis and it was associated with an increased mortality. Allopurinol is a medication intended to lower uric acid and therefore prevents gout attacks. Its metabolism is mainly renal, and some studies from the early 1960s demonstrated that it is also dialyzable. At the moment, we do not have strong evidence of the optimal dosage of allopurinol with modern techniques of dialysis. The hypothesis is that allopurinol would be more efficacious to lower uric acid if it was given after dialysis only. The investigators will then switch administration of allopurinol to bedtime for dialysis patients currently taking that medication. Dosage of uric acid will be performed to assess the efficacy of the intervention.

Inclusion Criteria:

• Subjects who receive chronic treatments of hemodialysis at Maisonneuve-Rosemont Hospital
• Subjects who take allopurinol for at least a month

Exclusion Criteria:

• Subjects who have had an acute gout attack in the past month
• Subjects with tumor lysis syndrome
• Sujects who have a history of hypersensitivity reaction to allopurinol
• Subjects with hepatic insufficiency
• Women who are pregnant or planning to become pregnant in the next three months