Gout flares are associated with serum concentrations of
urate above 0.42 mmol/L (7 mg/dL). Achieving and maintaining serum
urate below 0.36 mmol/L is considered an effective response to ULT. On an intention to treat basis, clinical trials indicate that
allopurinol at daily doses of 100 to 300 mg decreases serum
urate adequately in only about 40% of
gout patients while
febuxostat 80 mg daily reduces serum
urate adequately in approximately 70% of
gout patients. Higher doses of ULT may be required in patients receiving concomitant
diuretics. The addition of a
uricosuric agent to
allopurinol and
febuxostat therapy significantly increases the proportion of patients achieving adequate lowering of serum
urate. Finally, carriers of a genetic variant of the transporter, ABCG2 (BCRP), have a decreased response to
allopurinol. Careful examination of medication adherence, titration of doses, and the addition of
uricosuric agents increase the percentage of patients responding to
allopurinol and
febuxostat.