“Many had worried that if we target both the afferent and efferent arterioles simultaneously, it might increase the risk for acute kidney injury. What has been reassuring in both the recent data from the DAPA-HF trial and in recent meta-analysis was no evidence of increased risk for acute kidney injury with use of the SGLT2 inhibitor,” Dr. Rangaswami said in an interview. For example, a recent report on more than 39,000 Canadian patients with T2D who were at least 66 years old and newly begun on either an SGLT2 inhibitor or a different oral diabetes drug (a dipeptidyl peptidase–4 inhibitor), found a statistically significant 21% lower rate of acute kidney injury during the first 90 days on treatment with an SGLT2 inhibitor in a propensity score–matched analysis (CMAJ. 2020 Apr 6;192: e351-60).
Sara Freeman/MDedge News
Dr. Silvio Inzucchi
Much of the concern about possible acute kidney injury stemmed from a property that the SGLT2 inhibitors share with RAS inhibitors: They cause an initial, reversible decline in glomerular filtration rate (GFR), followed by longer-term nephron preservation, a pattern attributable to reduced intraglomerular pressure. The question early on was: “ ‘Does this harm the kidney?’ But what we’ve seen is that patients do better over time, even with this initial hit. Whenever you offload the glomerulus you cut barotrauma and protect renal function,” explained Silvio E. Inzucchi, MD, professor of medicine at Yale University, New Haven, Conn., and director of the Yale Medicine Diabetes Center.
Dr. Inzucchi cautioned, however, that a small number of patients starting treatment with an SGLT2 inhibitor may have their GFR drop too sharply, especially if their GFR was low to start with. “You need to be careful, especially at the lower end of the GFR range. I recheck renal function after 1 month” after a patient starts an SGLT2. Patients whose level falls too low may need to discontinue. He added that it’s hard to set a uniform threshold for alarm, and instead assess patients on a case-by-case basis, but “you need some threshold in mind, where you will stop” treatment.
A smarter diuretic
One of the most intriguing renal effects of SGLT2 inhibitors is their diuretic action. During a talk at the virtual ADA scientific sessions, cardiologist Jeffrey Testani, MD, called them “smart” diuretics, because their effect on diuresis is relatively modest but comes without the neurohormonal price paid when patients take conventional loop diuretics.
”Loop diuretics are particularly bad,” causing neurohormonal activation that includes norepinephrine, renin, and vasopressin, said Dr. Testani, director of heart failure research at Yale. They also fail to produce a meaningful drop in blood volume despite causing substantial natriuresis.
In contrast, SGLT2 inhibitors cause “moderate” natriuresis while producing a significant cut in blood volume. “The body seems content with this lower plasma volume without activating catecholamines or renin, and that’s how the SGLT2 inhibitors differ from other diuretics,” said Dr. Inzucchi.
The class also maintains serum levels of potassium and magnesium, produces significant improvements in serum uric acid levels, and avoids the electrolyte abnormalities, volume depletion, and acute kidney injury that can occur with conventional distal diuretics, Dr. Testani said.
In short, the SGLT2 inhibitors “are safe and easy-to-use diuretics,” which allows them to fill a “huge unmet need for patients with heart failure.” As evidence accumulates for the benefits of the drug class in patients with heart failure and renal disease, “uptake will be extensive,” Dr. Testani predicted, driven in part by how easy it is to add the class to existing cardiorenal drug regimens.
Other standard therapies for patients with heart failure with reduced ejection fraction (HFrEF) risk electrolyte abnormalities, renal dysfunction, significantly lower blood pressure, often make patients feel worse, and involve a slow and laborious titration process, Dr. Testani noted. The SGLT2 inhibitor agents avoid these issues, a property that has played out in quality of life assessments of patients with HFrEF who received a drug from this class.