medwireNews: Patients with gout are more likely to develop nephrolithiasis than population controls, but the majority of medications used frequently by gout patients do not alter this risk, according to the results of a Swedish healthcare registry study.
The researchers found that 29,968 patients with gout experienced 678 nephrolithiasis events between 2006 and 2012, whereas there were 2125 nephrolithiasis events among 138,678 age- and gender-matched controls.
These findings translated into corresponding incidence rates of 6.2 and 3.9 events per 1000 person–years, meaning that participants with gout were a significant 60% more likely to develop nephrolithiasis than those without, report Anton Landgren (University of Gothenburg, Sweden) and colleagues in Arthritis Research & Therapy.
Furthermore, after multivariable adjustment for age, gender, and other possible risk factors, treatment with thiazide diuretics, calcium channel blockers, statins, potassium-sparing diuretics, or renin-angiotensin–aldosterone inhibitors did not significantly modify the risk for first-time nephrolithiasis among patients with gout.
However, gout patients taking loop diuretics had a significantly lower risk for nephrolithiasis than those not taking these drugs (adjusted hazard ratio [HR]=0.71), and diabetes and obesity were associated with an increased risk for nephrolithiasis in an analysis of gout comorbidities (HR=1.57 and 1.55, respectively).
“Obesity and use of loop diuretics were identified as the only potentially modifiable risk factors for [nephrolithiasis] in gout,” say Landgren and colleagues, but they note that “increased use of the latter is associated with risk of exacerbation of gout.”
In contrast to the results of a previous study, the researchers found that allopurinol use was not significantly associated with nephrolithiasis among patients with gout (HR=1.01).
“Possible explanations for why we did not observe a protective effect of allopurinol, could partly be nonadherence and low dosing of urate-lowering therapy in clinical practice,” write the researchers.
Indeed, the doses of allopurinol used in the study were “low,” with 62% of patients taking the drug at a dose of 100 mg/day.
And the team suggests: “Had the dosing of allopurinol been optimized, aiming at treatment goals for serum uric acid levels, it is possible that the incidence of [nephrolithiasis] would have been lower in patients with gout.”
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