Research article
Adherence with urate-lowering therapies for the treatment of gout
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* Corresponding author: Leslie R Harrold Leslie.Harrold@umassmed.edu
1 Department of Medicine, the Meyers Primary Care Institute, 425 North Lake Avenue Worcester, MA 01605, USA
2 Department of Medicine, University of Massachusetts Medical School, 377 Plantation Street Worcester, MA 01605, USA
3 The HMO Research Network Center for Education and Research in Therapeutics, Department of Medicine, University of Massachusetts Medical School, 377 Plantation Street Worcester, MA 01605, USA
4 Department of Research, Kaiser Permanente, Colorado Institute for Health Research, PO Box 378066 Denver, CO 80237-8066, USA
5 Department of Medicine, Fallon Clinic, 425 North Lake Avenue Worcester, MA 01605, USA
Arthritis Research & Therapy 2009, 11:R46 doi:10.1186/ar2659
Published: 27 March 2009Abstract
Introduction
Adherence to urate-lowering drugs (ULDs) has not been well evaluated among those with gout. Our aim was to assess the level and determinants of non-adherence with ULDs prescribed for gout.
Methods
We identified persons using two integrated delivery systems aged 18 years or older with a diagnosis of gout who initiated use of allopurinol, probenecid or sulfinpyrazone from 1 January 2000 to 30 June 2006. Non-adherence was measured using the medication possession ratio (MPR) over the first year of therapy and defined as an MPR < 0.8. Descriptive statistics were calculated and logistic regression was used to estimate the strength of the association between patient characteristics and non-adherence.
Results
A total of 4,166 gout patients initiated ULDs; 97% received allopurinol. Median MPR for any ULD use was 0.68 (interquartile range (IQR) 0.64). Over half of the patients (56%) were non-adherent (MPR < 0.8). In adjusted analyses, predictors of poor adherence included younger age (odds ratio (OR) 2.43, 95% confidence interval (CI) 1.86 to 3.18 for ages <45 and OR 1.44, 95% CI 1.08 to 1.93 for ages 45 to 49), fewer comorbid conditions (OR 1.46, 95% CI 1.20 to 1.77), no provider visits for gout prior to urate-lowering drug initiation (OR 1.28, 95% CI 1.05 to 1.55), and use of non-steroidal anti-inflammatory drugs in the year prior to urate-lowering drug initiation (OR 1.15, 95% CI 1.00 to 1.31).
Conclusions
Non-adherence amongst gout patients initiating ULDs is exceedingly common, particularly in younger patients with less comorbidity and no provider visits for gout prior to ULD initiation. Providers should be aware of the magnitude of non-adherence with ULDs.