In this study, Singh et al identified a cohort of patients at the Minneapolis VA Medical Center database who received a new allopurinol or probenecid prescription between 1999 and 2003. Patients had to be followed by the VA two or more times over the year to ensure the VA had primarily responsibility for this medication management. The outcomes they examined included the percentage of patients receiving continuous allopurinol prescriptions, those who received colchicine or nonsteroidal antiinflammatroy drug (NSAID) prophylaxis with allopurinol initiation, the percentage who achieved the target serum uric acid (SUA) of ≤6.0, and the percentage who had colchicine or probenecid dosed for the presence of renal failure.
A cohort of 643 VA patients with a new allopurinol prescription managed by the VA was identified from a total of 3,658 patients with a gout diagnosis. The mean initial dose of allopurinol was 200 mg/day. A total of 125 patients receiving probenecid were identified, with over half of patients receiving 1,000 mg/day. The key results are depicted in Table 1 (above). Only 46% of patients filled a continuous prescription of allopurinol. As compliance with allopurinol dosing is notoriously low, this is not that surprising. What is eye opening, however, is the percentage of patients on allopurinol who did not have their SUA checked before death or when the study period ended (61%), and the fact that that only 20% reached the target SUA. Of those who did not achieve the target SUA, only 37% had an allouprinol dose change. Conversely, 24% of patients had a change in their allopurinol dose without a documented SUA. In regards to prophylaxis for acute gout flare with the initiation of allopurinol, 52% of patients did not receive a prescription for colchicine or NSAID at or before the onset of allopurinol.
The authors then performed multivariate analysis to examine associations between patient characteristics and the outcome measures. Allopurinol was discontinued less in patients with more primary care or rheumatology visits (an increase of 2.7 visits per year was associated with a 12% decrease in medication discontinuation). Patients with more outpatient visits were more likely to receive colchicine prophylaxis. Patients in rheumatology clinics had a 34% rate of colchicine prophylaxis, compared with other clinics with a rate of 6–8%. Patients with higher Charlson Comorbidity Index, an index assessing one-year mortality attributable to comorbidities, were less likely to obtain a target SUA.With respect to probenecid, only 42% of subjects had a subsequent creatinine check. In patients experiencing an episode of renal insufficiency while on probenecid, 77% had the drug stopped appropriately, while the remainder resolved their episode.
