What are the most common reasons for inadequate response of serum uric acid to allopurinol?
Poor adherence and under-dosing of allopurinol by physicians (failure to titrate dose to goal serum uric acid level) are the two most common causes. Adherence may be as low as 50%. Patients are asymptomatic in the intercritical period, and there is lack of understanding about the need for daily long-term medication. Adherence can be evaluated by checking serum oxipurinol levels in patients on allopurinol. About half of patients do not achieve a serum uric acid goal of <= 6.0 at an allopurinol dose of 300 mg. Some patients do have “resistance” to allopurinol, but this is less common.
