Pharmacology · Diabetes Pharmacology

SGLT-2 Inhibitors

Mechanism, cardiovascular and renal outcome trials, and safety

SGLT-2 inhibitors block sodium-glucose cotransporter 2 in the S1 segment of the proximal tubule, preventing reabsorption of approximately 90% of filtered glucose and causing glucosuria; the accompanying osmotic natriuresis lowers plasma volume and reduces intraglomerular pressure through tubuloglomerular feedback — the same mechanism that produces blood pressure reduction (3–5 mmHg) also reduces hyperfiltration, which is why the renal protective effect occurs even in patients without diabetes and even at eGFR levels where glucose lowering is minimal.
The cardiovascular benefit of SGLT-2 inhibitors is mechanistically distinct from GLP-1 agonists — the primary driver is hemodynamic (reduced preload and afterload through volume contraction, reduced sympathetic activity, reduced arterial stiffness) rather than antiatherosclerotic; this explains why the heart failure benefit is the most consistent finding across all CVOTs and why the EMPEROR-Preserved and DAPA-HF/EMPEROR trials showed benefit across the full ejection fraction spectrum, while atherosclerotic MACE benefit is more variable across agents.
The EMPA-REG OUTCOME trial (empagliflozin) was the first to show cardiovascular death reduction in diabetic patients, with a 38% reduction in CV death observed within weeks of starting treatment — far too rapid to be explained by glycemic improvement or plaque regression, confirming the hemodynamic mechanism; subsequent trials with dapagliflozin, canagliflozin, and ertugliflozin replicated heart failure benefit but showed more heterogeneous MACE results.
The renal protection profile of SGLT-2 inhibitors is now established across two distinct populations: CREDENCE (canagliflozin) and EMPA-KIDNEY (empagliflozin) demonstrated significant reductions in progression to end-stage kidney disease in patients with CKD, the latter even including patients with eGFR as low as 20–45 mL/min who derive no clinically meaningful glucose lowering — confirming that the renal benefit is glucose-independent and operates entirely through hemodynamic and anti-inflammatory mechanisms.
The most clinically significant safety signals are DKA (often euglycemic, meaning glucose is near-normal despite ketosis — a trap for clinicians who do not check ketones in unwell patients on SGLT-2 inhibitors), and the requirement to hold the drug perioperatively: SGLT-2 inhibitors should be withheld at least 3–4 days before major surgery to prevent surgery-associated euglycemic DKA, which has been fatal in several reported cases.

Abbreviations: SGLT-2 = sodium-glucose cotransporter 2 · DKA = diabetic ketoacidosis · HFrEF = heart failure with reduced ejection fraction · HFpEF = heart failure with preserved ejection fraction · MACE = major adverse cardiovascular events · eGFR = estimated glomerular filtration rate · UTI = urinary tract infection · CV = cardiovascular

Mechanism and Downstream Effects

Primary Mechanism

Proximal Tubule Glucose Block

Block SGLT-2 in S1 proximal tubule → prevents reabsorption of ~90% filtered glucose
Glucosuria (~70–80 g glucose excreted per day) → ~0.5–1% HbA1c reduction
Glucose-independent mechanism: renal and heart failure benefits occur even when glucose-lowering effect is minimal (low eGFR)
Osmotic natriuresis → plasma volume contraction → reduced preload and afterload

Downstream Effects

Hemodynamic and Tubular

Intraglomerular pressure ↓ via tubuloglomerular feedback (macula densa) → renal protection
Blood pressure reduction 3–5 mmHg (systolic) — no reflex tachycardia
Weight loss 1–3 kg — mostly fluid initially, then adipose
Mild hematocrit rise — volume contraction increases red cell concentration
Ketogenesis mildly increased — reduced insulin, increased glucagon, enhanced lipolysis

Cardiovascular and Renal Outcome Trials

Trial	Agent	Population	CV Result	Renal Result	Key Finding
EMPA-REG	Empagliflozin	T2DM + high CV risk	MACE ↓	Renal ↓	38% CV death reduction — rapid onset (weeks); landmark trial establishing class CV benefit
CANVAS	Canagliflozin	T2DM + high CV risk	MACE ↓	Renal ↓	Lower extremity amputation signal (2× risk) — mechanism unclear; monitor
CREDENCE	Canagliflozin	T2DM + CKD	MACE ↓	ESKD ↓	First dedicated renal outcome trial; terminated early for efficacy; eGFR as low as 30 enrolled
DECLARE	Dapagliflozin	T2DM + risk factors	Neutral	Renal ↓	Primary prevention population; HF hospitalization significantly reduced despite neutral MACE
DAPA-HF	Dapagliflozin	HFrEF (with/without DM)	HF ↓	—	Benefit in HF regardless of diabetes status — first major HF trial including non-diabetic patients
EMPEROR-R/P	Empagliflozin	HFrEF and HFpEF	HF ↓	Renal ↓	Benefit across full EF spectrum — class-wide heart failure indication regardless of EF or diabetes status
EMPA-KIDNEY	Empagliflozin	CKD (eGFR 20–45)	CV ↓	ESKD ↓	Renal benefit confirmed at very low eGFR where glucose-lowering is absent — purely hemodynamic/anti-inflammatory

Safety Profile

Most Critical — Must Counsel

Euglycemic DKA

DKA can occur with near-normal glucose — "euglycemic DKA"; clinicians unfamiliar with this presentation may miss the diagnosis
Risk factors: prolonged fasting, major surgery, heavy alcohol use, very low carbohydrate diet, type 1 diabetes (off-label use)
Hold 3–4 days before major surgery — perioperative euglycemic DKA has been fatal
Symptomatic unwell patient on SGLT-2 inhibitor: check ketones regardless of glucose level

Common and Rare Infections

Genital and Urinary Infections

Genital mycotic infections: 3–8× increased risk — glucosuria creates ideal culture environment for Candida
Fournier gangrene (necrotizing fasciitis of perineum): rare but life-threatening — FDA black box warning; early recognition essential
UTI: mild increase; recurrent UTI may warrant switching to alternate class
Genital infections generally respond to standard antifungal treatment

Contraindications and Dose Limits

Renal Function Limits

Glucose-lowering indication: generally avoid if eGFR <45 (agent-specific) — insufficient glucose delivery to proximal tubule
Heart failure and CKD indications: continue to lower eGFR thresholds (20–30 depending on agent and indication)
Empagliflozin/dapagliflozin: approved for HF and CKD at eGFR where glucose effect is absent
Canagliflozin: increased amputation risk — monitor lower extremities, especially in peripheral vascular disease

SGLT-2 Inhibitors — Expanding Beyond Diabetes

SGLT-2 inhibitors are now firmly established as cardioprotective and nephroprotective agents independent of their glucose-lowering effect. The FDA has approved empagliflozin and dapagliflozin for heart failure regardless of ejection fraction (HFrEF and HFpEF) and regardless of diabetes status. Empagliflozin and canagliflozin are approved to reduce CKD progression in patients with and without diabetes.

This means SGLT-2 inhibitors should be considered in any patient with established HF or CKD as a disease-modifying therapy — not just as an add-on for glucose control. The glucose-lowering effect is a secondary benefit in these populations. When prescribing, choose the agent with the strongest outcome data for the patient's specific condition: empagliflozin or dapagliflozin for HF, empagliflozin or canagliflozin for CKD.

Suggested References

Author / Source	Title	Publication
Katzung BG, ed.	Basic and Clinical Pharmacology, 15th ed. — Chapter 41: Pancreatic Hormones and Antidiabetic Drugs	McGraw-Hill; 2021
Brunton L, Knollmann B, Hilal-Dandan R, eds.	Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. — Chapter 45: Endocrine Pancreas and Pharmacotherapy of Diabetes Mellitus and Hypoglycemia	McGraw-Hill; 2023
Vallon V, Thomson SC	Targeting renal glucose reabsorption to treat hyperglycemia: the pleiotropic effects of SGLT-2 inhibition	Diabetologia. 2017;60(2):215–225
Cherney DZI et al	Renal hemodynamic effect of sodium-glucose cotransporter 2 inhibition in patients with type 1 diabetes mellitus	Circulation. 2014;129(5):587–597
Neal B et al (CANVAS)	Canagliflozin and cardiovascular and renal events in type 2 diabetes	N Engl J Med. 2017;377(7):644–657
Perkovic V et al (CREDENCE)	Canagliflozin and renal outcomes in type 2 diabetes and nephropathy	N Engl J Med. 2019;380(24):2295–2306
Packer M et al (EMPEROR-Reduced)	Cardiovascular and renal outcomes with empagliflozin in heart failure	N Engl J Med. 2020;383(15):1413–1424
Cannon CP et al (VERTIS-CV)	Cardiovascular outcomes with ertugliflozin in type 2 diabetes	N Engl J Med. 2020;383(15):1425–1435
Zinman B et al (EMPA-REG OUTCOME)	Empagliflozin, cardiovascular outcomes, and mortality in type 2 diabetes	N Engl J Med. 2015;373(22):2117–2128
Anker SD et al (EMPEROR-Preserved)	Empagliflozin in heart failure with a preserved ejection fraction	N Engl J Med. 2021;385(16):1451–1461
Wiviott SD et al (DECLARE-TIMI 58)	Dapagliflozin and cardiovascular outcomes in type 2 diabetes	N Engl J Med. 2019;380(4):347–357
McMurray JJV et al (DAPA-HF)	Dapagliflozin in patients with heart failure and reduced ejection fraction	N Engl J Med. 2019;381(21):1995–2008
Lopaschuk GD, Verma S	Mechanisms of cardiovascular benefits of sodium glucose co-transporter 2 inhibitors	JACC Basic Transl Sci. 2020;5(6):632–644
EMPA-KIDNEY Collaborative Group	Empagliflozin in patients with chronic kidney disease	N Engl J Med. 2023;388(2):117–127
Bersoff-Matcha SJ et al	Fournier gangrene associated with sodium-glucose cotransporter-2 inhibitors	Ann Intern Med. 2019;170(11):764–769
American Diabetes Association	Standards of Care in Diabetes—2024	Diabetes Care. 2024;47(Suppl 1):S1–S321