Abstract
Background: Patients with chronic gout require sustained treatment with urate-lowering drugs (ULDs). Little is known regarding adherence to medication treatment for gout. Our aim was to assess the level and determinants of adherence with ULDs prescribed for chronic gout.
Methods: A retrospective cohort study was conducted using administrative data from two health plans participating in the HMO Research Network Center for Education and Research on Therapeutics. We identified all persons 18 years or older with a diagnosis of gout who initiated use of a ULD (allopurinol or probenecid) from January 1, 2000 through June 2006 who were enrolled for at least 12 months after the first ULD dispensing. Adherence was measured based on the medication possession ratio (MPR) which was determined by the sum of the day’s supply of drug therapy from the first dispensing to the end of the 12-month period. Covariates included age, sex, comorbid illnesses and medications associated with gout, concurrent treatments for gout and the Charlson comorbidity index.
Results: Preliminary data for 627 gout patients at one health plan indicated the median MPR was 0.49 (±0.32) for allopurinol and 0.48 (±0.37) for probenecid. Factors associated with poor adherence (defined as an MPR <0.80) included younger age (<45 yrs), fewer comorbid conditions, use of nonsteroidal anti-inflammatory drugs (NSAIDs) prior to initiation of a ULD, and use of a glucocorticoid or NSAID after initiating a ULD.
Conclusions: Nonadherence is common in gout, particularly in young men without other comorbidities. In addition, it appears those with more active gout (based on dispensings of NSAIDs and glucocorticoids) are less adherent.
- Received September 11, 2008.
