than patients who received placebo during a median 1.5 years of treatment.
These findings are from an analysis of pooled data from phase 1-4 clinical trials of empagliflozin for blood glucose control in 15,081 patients with type 2 diabetes.
Priyadarshini Balasubramanian, MD, presented the study as a poster at the annual meeting of the Endocrine Society; the study also was published online in the Journal of Clinical Endocrinology & Metabolism.
The researchers acknowledge this was a retrospective, post-hoc analysis and that urolithiasis – a stone in the urinary tract, which includes nephrolithiasis, a kidney stone – was an adverse event, not a primary or secondary outcome.
Also, the stone composition, which might help explain how the drug may affect stone formation, is unknown.
Therefore, “dedicated randomized prospective clinical trials are needed to confirm these initial observations in patients both with and without type 2 diabetes,” said Dr. Balasubramanian, a clinical fellow in the section of endocrinology & metabolism, department of internal medicine at Yale University, New Haven, Conn.
However, “if this association is proven, empagliflozin may be used to decrease the risk of kidney stones at least in those with type 2 diabetes, but maybe also in those without diabetes,” Dr. Balasubramanian said in an interview.
Further trials are also needed to determine if this is a class effect, which is likely, she speculated, and to unravel the potential mechanism.
This is important because of the prevalence of kidney stones, which affect up to 15% of the general population and 15%-20% of patients with diabetes, she explained.
‘Provocative’ earlier findings
The current study was prompted by a recent observational study by Kasper B. Kristensen, MD, PhD, and colleagues.
Because SGLT2 inhibitors increase urinary glucose excretion through reduced renal reabsorption of glucose leading to osmotic diuresis and increased urinary flow, they hypothesized that these therapies “may reduce the risk of upper urinary tract stones (nephrolithiasis) by reducing the concentration of lithogenic substances in urine.”
Using data from Danish Health registries, they matched 12,325 individuals newly prescribed an SGLT2 inhibitor 1:1 with patients newly prescribed a glucagonlike peptide-1 (GLP1) agonist, another new class of drugs for treating type 2 diabetes.
They found a hazard ratio of 0.51 (95% confidence interval, 0.37-0.71) for incident nephrolithiasis and a hazard ratio of 0.68 (95% CI, 0.48-0.97) for recurrent nephrolithiasis for patients taking SGLT2 inhibitors versus GLP-1 agonists.
These findings are “striking,” according to Dr. Balasubramanian and colleagues. However, “these data, while provocative, were entirely retrospective and therefore possibly prone to bias,” they add.
Pooled data from 20 trials
The current study analyzed data from 20 randomized controlled trials of glycemic control in type 2 diabetes, in which 10,177 patients had received empagliflozin 10 mg or 25 mg and 4,904 patients had received placebo.
Most patients (46.5%) had participated in the EMPA-REG OUTCOMES trial, which also had the longest follow-up (2.6 years).
The researchers identified patients with a new stone from the urinary tract (including the kidney, ureter, and urethra). Patients had received either the study drug for a median of 543 days or placebo for a median of 549 days.
During treatment, 104 of 10,177 patients in the pooled empagliflozin groups and 79 of 4,904 patients in the pooled placebo groups developed a stone in the urinary tract.
This was equivalent to 0.63 new urinary-tract stones per 100 patient-years in the pooled empagliflozin groups versus 1.01 new urinary-tract stones per 100 patient-years in the pooled placebo groups.
The incidence rate ratio was 0.64 (95% CI, 0.48-0.86), in favor of empagliflozin.
When the analysis was restricted to new kidney stones, the results were similar: 75 of 10,177 patients in the pooled empagliflozin groups and 57 of 4,904 patients in the pooled placebo groups developed a kidney stone.
This was equivalent to 0.45 new kidney stones per 100 patient-years in the pooled empagliflozin groups versus 0.72 new kidney stones per 100 patient-years in the pooled placebo groups.
The IRR was 0.65 (95% CI, 0.46-0.92), in favor of empagliflozin.