Medical Pharmacology: Chapter 29 — Diabetes Pharmacology -- Module 6 — SGLT-2 Inhibitors: Mechanisms, Outcome Trials, and Clinical Framework

Chapter 29 — Diabetes Pharmacology — Module 6 — SGLT-2 Inhibitors: Mechanisms, Outcome Trials, and Clinical Framework

1. [CASE 1 — QUESTION 1] A 64-year-old man (J.M.) with type 2 diabetes mellitus and heart failure with reduced ejection fraction (left ventricular ejection fraction 32%) is seen in clinic. He is on guideline-directed medical therapy including carvedilol, sacubitril/valsartan, and spironolactone, and his loop diuretic dose is stable. His estimated glomerular filtration rate (eGFR) is 35 mL/min/1.73 m2, HbA1c is 7.6%, and he has no peripheral arterial disease or prior amputation. His clinician wants to further reduce his risk of heart failure hospitalization. Which addition is most appropriate?

A) No SGLT-2 inhibitor can be added, because his eGFR of 35 is below the glycemic threshold of approximately 45 mL/min/1.73 m2
B) Ertugliflozin, because it has the strongest dedicated heart failure outcome data in the class
C) Dapagliflozin or empagliflozin, because both reduce heart failure hospitalization and their heart failure indication extends to a cardiorenal eGFR floor of roughly 20 to 25 mL/min/1.73 m2, permitting use at an eGFR of 35
D) A second loop diuretic, because adding an SGLT-2 inhibitor is contraindicated in patients already taking a mineralocorticoid receptor antagonist
E) Canagliflozin, because it is the preferred heart failure agent and carries the lowest amputation risk of the class

ANSWER: C

Rationale:

J.M. has heart failure with reduced ejection fraction on optimized guideline-directed therapy with an eGFR of 35 mL/min/1.73 m2. Dapagliflozin and empagliflozin reduce heart failure hospitalization and cardiovascular death, and their heart failure indication extends down to a cardiorenal eGFR floor of roughly 20 to 25 mL/min/1.73 m2, so either can be added at an eGFR of 35.

Option A: Option A is incorrect because the approximately 45 mL/min/1.73 m2 figure is the glycemic threshold, not the cardiorenal floor governing the heart failure indication.
Option B: Option B is incorrect because ertugliflozin has no dedicated heart failure outcome benefit or heart failure indication.
Option D: Option D is incorrect because SGLT-2 inhibitors are not contraindicated with a mineralocorticoid receptor antagonist, and a second loop diuretic would not provide the outcome benefit sought.
Option E: Option E is incorrect because canagliflozin is not the preferred heart failure agent and carries the canagliflozin-specific amputation signal rather than the lowest amputation risk.

2. [CASE 1 — QUESTION 2] Continuing with the same patient. J.M. is started on dapagliflozin 10 mg daily. Two weeks later his eGFR has declined from 35 to 31 mL/min/1.73 m2. He is asymptomatic, euvolemic on examination, and his potassium is normal. How should this change be interpreted and managed?

A) This is an expected, largely reversible hemodynamic dip from tubuloglomerular feedback (increased distal sodium delivery constricts the afferent arteriole, lowering intraglomerular pressure), the same effect that underlies long-term renoprotection; dapagliflozin should be continued with routine monitoring
B) This indicates acute interstitial nephritis and the drug must be stopped permanently and never re-trialed
C) This reflects efferent arteriolar constriction that raises intraglomerular pressure and signals impending kidney failure requiring urgent dialysis planning
D) This is unexplained and most consistent with laboratory error that can be disregarded without monitoring
E) This indicates volume overload from sodium retention, and the dapagliflozin dose should be increased to enhance diuresis

ANSWER: A

Rationale:

A modest decline in eGFR shortly after starting an SGLT-2 inhibitor in an asymptomatic, euvolemic patient is an expected, largely reversible hemodynamic effect: increased distal sodium delivery activates tubuloglomerular feedback, constricting the afferent arteriole and lowering intraglomerular pressure, the same mechanism that produces long-term renoprotection. The drug should be continued with routine monitoring.

Option B: Option B is incorrect because this is a predictable hemodynamic dip, not acute interstitial nephritis mandating permanent discontinuation.
Option C: Option C is incorrect because it inverts the mechanism: SGLT-2 inhibition constricts the afferent arteriole and lowers intraglomerular pressure rather than raising it.
Option D: Option D is incorrect because the change has a clear mechanistic explanation and warrants monitoring rather than dismissal.
Option E: Option E is incorrect because SGLT-2 inhibitors cause natriuresis and volume reduction, not sodium retention, so a volume-overload explanation and a dose increase are both wrong.

3. [CASE 1 — QUESTION 3] Continuing with the same patient. J.M. asks how a "diabetes pill" helps his heart failure when his blood sugars were already reasonably controlled. Which explanation best captures the principal heart failure mechanism of dapagliflozin?

A) It acts as a direct positive inotrope, increasing myocardial contractility through enhanced calcium-induced calcium release
B) It works only by lowering blood glucose, so its heart failure benefit is entirely a consequence of improved glycemic control
C) It blocks beta-adrenergic receptors, slowing heart rate and reducing myocardial oxygen demand as its main heart failure action
D) It reduces preload through osmotic diuresis and natriuresis and modestly reduces afterload through blood pressure lowering, achieving these volume effects without the neurohormonal (renin-angiotensin and sympathetic) activation that usually accompanies aggressive diuresis
E) It causes coronary vasodilation that increases myocardial oxygen delivery, independent of any change in volume status

ANSWER: D

Rationale:

The principal heart failure mechanism of an SGLT-2 inhibitor is hemodynamic and largely independent of glucose lowering: preload reduction through osmotic diuresis and natriuresis, with modest afterload reduction from blood pressure lowering, and notably these volume effects occur without the neurohormonal (renin-angiotensin and sympathetic) activation that typically accompanies aggressive loop diuresis.

Option A: Option A is incorrect because the class is not a direct positive inotrope and does not act through enhanced calcium-induced calcium release.
Option B: Option B is incorrect because the heart failure benefit is substantially independent of glycemic improvement, as shown by benefit even in non-diabetic patients.
Option C: Option C is incorrect because beta-adrenergic blockade is not the SGLT-2 inhibitor mechanism.
Option E: Option E is incorrect because coronary vasodilation increasing oxygen delivery independent of volume status is not the mechanism; volume unloading and the metabolic effects are central.

4. [CASE 1 — QUESTION 4] Continuing with the same patient. Two years later, J.M. develops peripheral arterial disease with a non-healing foot ulcer. A records review shows that, at an outside visit, his SGLT-2 inhibitor had been switched to canagliflozin. Considering agent-specific safety, what is the most appropriate adjustment?

A) Continue canagliflozin unchanged, because its lower-extremity effects improve perfusion in peripheral arterial disease
B) Switch from canagliflozin back to dapagliflozin or empagliflozin, because the increased lower-extremity amputation signal is considered largely canagliflozin-specific, making a different agent more prudent in a patient with peripheral arterial disease and an active foot ulcer
C) Discontinue all SGLT-2 inhibitors permanently, because the amputation signal is a uniform class effect that applies to every agent equally
D) Switch to ertugliflozin, because it has the strongest heart failure outcome data and the lowest amputation risk
E) Increase the canagliflozin dose to 300 mg, because higher doses mitigate the amputation risk

ANSWER: B

Rationale:

The increased lower-extremity amputation signal was identified with canagliflozin and is considered largely canagliflozin-specific rather than a consistent class effect. In a patient who now has peripheral arterial disease and an active foot ulcer, switching from canagliflozin back to dapagliflozin or empagliflozin (both of which provide the needed heart failure benefit) is the prudent choice, alongside foot care.

Option A: Option A is incorrect because the canagliflozin signal reflects increased amputation risk, not improved perfusion.
Option C: Option C is incorrect because the signal is not a uniform class effect, so permanent discontinuation of all agents would needlessly forgo heart failure benefit.
Option D: Option D is incorrect because ertugliflozin lacks dedicated heart failure outcome benefit and is not the appropriate substitute here.
Option E: Option E is incorrect because increasing the canagliflozin dose does not mitigate amputation risk and, if anything, raises concern; the appropriate step is to change agents.

5. [CASE 2 — QUESTION 1] A 47-year-old woman (R.K.) with type 2 diabetes mellitus has been taking empagliflozin 10 mg daily for two years with good tolerance. She presents to the emergency department with two days of nausea, vomiting, and poor oral intake during an influenza-like illness. She appears unwell and mildly tachypneic. Her plasma glucose is 190 mg/dL. The covering physician is reassured by the near-normal glucose. What is the most appropriate immediate step?

A) Discharge her with antiemetics, since the near-normal glucose excludes diabetic ketoacidosis
B) Measure serum or urine ketones and a blood gas, hold the empagliflozin, and evaluate for euglycemic diabetic ketoacidosis despite the near-normal glucose
C) Administer a large intravenous dextrose bolus, since a glucose of 190 mg/dL signals impending hypoglycemia
D) Increase the empagliflozin dose to control glucose during the acute illness
E) Attribute the symptoms to a urinary tract infection and begin oral antibiotics without further metabolic testing

ANSWER: B

Rationale:

R.K. is on an SGLT-2 inhibitor and has nausea, vomiting, and reduced intake during an acute illness, the classic precipitating setting for euglycemic diabetic ketoacidosis. Because ketoacidosis can develop with only modestly elevated glucose, the correct step is to measure ketones and a blood gas, hold the drug, and evaluate for euglycemic ketoacidosis despite the near-normal glucose.

Option A: Option A is incorrect because a near-normal glucose does not exclude euglycemic ketoacidosis, which is the central diagnostic pitfall.
Option C: Option C is incorrect because a glucose of 190 mg/dL is not hypoglycemia, and dextrose alone does not address the ketoacidosis evaluation.
Option D: Option D is incorrect because increasing the dose during a precipitating illness worsens ketoacidosis risk.
Option E: Option E is incorrect because attributing the presentation to a urinary tract infection without metabolic testing risks missing euglycemic ketoacidosis.

6. [CASE 2 — QUESTION 2] Continuing with the same patient. R.K.'s labs confirm a high anion-gap metabolic acidosis with elevated beta-hydroxybutyrate and a glucose of 190 mg/dL. Which mechanism best explains why her glucose is only modestly elevated despite frank ketoacidosis?

A) Renal bicarbonate wasting directly lowers glucose while generating the acidosis, independent of ketones
B) Excess insulin secretion is suppressing hepatic glucose output, producing low-normal glucose with a coincidental acidosis
C) Lactic acid accumulation, not ketone production, is generating the anion gap, and glucose is normal because ketogenesis is absent
D) The acidosis is caused by the influenza illness alone, and the SGLT-2 inhibitor has no role in the metabolic disturbance
E) Relative insulin deficiency with glucagon excess drives hepatic ketogenesis, while the glycosuric effect of the SGLT-2 inhibitor continuously removes glucose in the urine and prevents marked hyperglycemia, yielding ketoacidosis with only modestly elevated glucose

ANSWER: E

Rationale:

Euglycemic diabetic ketoacidosis on an SGLT-2 inhibitor arises because relative insulin deficiency with glucagon excess drives hepatic ketogenesis, while the drug's glycosuric effect continuously removes glucose in the urine and prevents marked hyperglycemia; the result is ketoacidosis with only modestly elevated glucose.

Option A: Option A is incorrect because the anion gap is generated by ketone (beta-hydroxybutyrate) accumulation, not by renal bicarbonate wasting lowering glucose.
Option B: Option B is incorrect because the process reflects relative insulin deficiency driving ketogenesis, not excess insulin suppressing glucose output.
Option C: Option C is incorrect because the elevated beta-hydroxybutyrate indicates a ketoacidosis, not a lactic acidosis with absent ketogenesis.
Option D: Option D is incorrect because the SGLT-2 inhibitor is central to the euglycemic pattern; the illness is a precipitant but does not explain the glucose-ketone dissociation on its own.

7. [CASE 2 — QUESTION 3] Continuing with the same patient. As R.K. recovers, she asks what circumstances make this complication more likely so she can avoid it in future. Which set of precipitants is most accurate for euglycemic diabetic ketoacidosis on an SGLT-2 inhibitor?

A) High-carbohydrate overfeeding and sedentary behavior, which drive insulin excess and ketosis
B) Routine well-controlled outpatient maintenance with normal eating, which is the highest-risk state
C) States of absolute or relative insulin deficiency such as acute illness, reduced oral intake, surgery, excessive alcohol intake, and very-low-carbohydrate (ketogenic) diets
D) Chronic overhydration and high salt intake, which expand volume and promote ketogenesis
E) Discontinuing the drug, which paradoxically triggers ketoacidosis more often than continuing it

ANSWER: C

Rationale:

Euglycemic diabetic ketoacidosis on an SGLT-2 inhibitor is precipitated by states of absolute or relative insulin deficiency: acute illness, reduced oral intake, surgery, excessive alcohol intake, and very-low-carbohydrate (ketogenic) diets, all of which promote glucagon-driven ketogenesis.

Option A: Option A is incorrect because high-carbohydrate overfeeding does not drive the insulin-deficient, ketogenic state that precipitates this complication.
Option B: Option B is incorrect because stable, well-fed outpatient maintenance is not the high-risk state; the risk rises with the insulin-deficient precipitants listed.
Option D: Option D is incorrect because overhydration and high salt intake are not recognized precipitants of euglycemic ketoacidosis.
Option E: Option E is incorrect because appropriately holding the drug during precipitating circumstances reduces, rather than triggers, the risk.

8. [CASE 2 — QUESTION 4] Continuing with the same patient. R.K. is treated and improves. The team plans her discharge and the future of her empagliflozin. Which plan is most appropriate?

A) Manage the acute episode with insulin, intravenous fluids, and glucose as needed while the empagliflozin is held, and resume the empagliflozin only after she is eating and drinking normally with negative ketones and no ongoing acute illness
B) Resume empagliflozin immediately at a doubled dose to compensate for the days it was held
C) Continue empagliflozin throughout the acute ketoacidosis, since stopping it would worsen glycemic control
D) Permanently prohibit any future SGLT-2 inhibitor use and document an absolute lifelong contraindication for a single precipitated episode
E) Replace empagliflozin with a second SGLT-2 inhibitor added on top, to spread the glycosuric load across two agents

ANSWER: A

Rationale:

The correct approach is to treat the acute euglycemic ketoacidosis with insulin, fluids, and glucose as needed while holding the SGLT-2 inhibitor, and to resume it only once she is eating and drinking normally with negative ketones and no ongoing acute illness. This mirrors the sick-day and perioperative logic for the class.

Option B: Option B is incorrect because resuming at a doubled dose is inappropriate and would increase recurrence risk.
Option C: Option C is incorrect because the drug should be held during the acute ketoacidosis, not continued.
Option D: Option D is incorrect because a single precipitated episode does not establish an absolute lifelong contraindication; sick-day rules and careful counseling typically allow cautious future use.
Option E: Option E is incorrect because two SGLT-2 inhibitors should never be combined.

9. [CASE 3 — QUESTION 1] A 76-year-old woman (E.T.) has heart failure with preserved ejection fraction (left ventricular ejection fraction 60%) with recurrent dyspnea, peripheral edema, and a prior heart failure hospitalization. She does NOT have diabetes and her HbA1c is 5.4%. She also has chronic kidney disease. Her clinician seeks a therapy proven to reduce the composite of cardiovascular death or heart failure hospitalization in her condition. Which agent is appropriate?

A) No SGLT-2 inhibitor is appropriate, because their benefit is limited to reduced ejection fraction heart failure
B) No SGLT-2 inhibitor is appropriate, because she has no diabetes and lacks a glycemic indication
C) A thiazolidinedione, which is the agent proven to reduce events in preserved ejection fraction heart failure
D) Empagliflozin, which reduced the composite of cardiovascular death or heart failure hospitalization in preserved ejection fraction heart failure regardless of diabetes status
E) Digoxin, which is the only agent shown to reduce the cardiovascular death or heart failure hospitalization composite in preserved ejection fraction heart failure

ANSWER: D

Rationale:

Empagliflozin reduced the composite of cardiovascular death or heart failure hospitalization in heart failure with preserved ejection fraction, and this benefit applies regardless of diabetes status, making it appropriate for E.T. despite the absence of diabetes.

Option A: Option A is incorrect because the benefit extends to preserved ejection fraction heart failure, not only reduced ejection fraction.
Option B: Option B is incorrect because the heart failure indication does not require diabetes or a glycemic indication.
Option C: Option C is incorrect because thiazolidinediones are not proven in preserved ejection fraction heart failure and can worsen fluid retention.
Option E: Option E is incorrect because digoxin has not been shown to reduce the cardiovascular death or heart failure hospitalization composite in preserved ejection fraction heart failure; empagliflozin has.

10. [CASE 3 — QUESTION 2] Continuing with the same patient. E.T.'s eGFR is 30 mL/min/1.73 m2 with albuminuria. A colleague worries that empagliflozin cannot be used because the eGFR is well below 45. How should the eGFR threshold be applied here?

A) The colleague is correct; an eGFR of 30 is below all usable thresholds, so empagliflozin cannot be started
B) The approximately 45 mL/min/1.73 m2 figure is the glycemic threshold; empagliflozin's heart failure and chronic kidney disease indications extend to a lower cardiorenal floor of roughly 20 to 25 mL/min/1.73 m2, so an eGFR of 30 is acceptable for these indications
C) A universal floor of 60 mL/min/1.73 m2 applies to all SGLT-2 inhibitors and all indications, so neither the heart failure nor the chronic kidney disease indication can be served here
D) The eGFR threshold depends only on the agent and never on the indication, so empagliflozin has one fixed floor regardless of why it is used
E) The eGFR must first be raised above 45 before empagliflozin can be considered, because that threshold applies to every indication

ANSWER: B

Rationale:

The eGFR floor is indication-specific. The approximately 45 mL/min/1.73 m2 figure is the glycemic threshold, whereas empagliflozin's heart failure and chronic kidney disease (CKD) indications extend to a lower cardiorenal floor of roughly 20 to 25 mL/min/1.73 m2. With an eGFR of 30, E.T. is above that cardiorenal floor, so empagliflozin is acceptable for her heart failure and CKD indications.

Option A: Option A is incorrect because an eGFR of 30 is not below the cardiorenal floor that governs these indications.
Option C: Option C is incorrect because there is no universal 60 mL/min/1.73 m2 floor across all agents and indications.
Option D: Option D is incorrect because the floor is not agent-only; the same agent has different floors for glycemic versus cardiorenal indications.
Option E: Option E is incorrect because the approximately 45 threshold is glycemic-specific and does not govern the cardiorenal indications, so raising eGFR above 45 is not required.

11. [CASE 3 — QUESTION 3] Continuing with the same patient. A trainee asks how empagliflozin can help when E.T.'s ejection fraction is normal. Which synthesis best explains benefit in preserved ejection fraction heart failure?

A) Benefit is explained solely by raising the ejection fraction further through direct positive inotropy
B) Benefit is explained entirely by low-density lipoprotein lowering and plaque regression reversing diastolic dysfunction
C) Benefit is explained by potent direct coronary vasodilation that increases oxygen supply independent of loading conditions
D) Benefit is explained by strong renin-angiotensin and sympathetic activation augmenting contractility during diuresis
E) Benefit reflects mechanisms largely independent of ejection fraction: preload reduction through osmotic diuresis and natriuresis without neurohormonal activation, reduced epicardial fat and pericardial constraint, anti-fibrotic effects, and a metabolic shift toward more oxygen-efficient ketone (beta-hydroxybutyrate) oxidation in the failing myocardium

ANSWER: E

Rationale:

Benefit in preserved ejection fraction heart failure reflects mechanisms that operate largely independent of ejection fraction: preload reduction through osmotic diuresis and natriuresis without the neurohormonal activation of aggressive diuresis, reduced epicardial fat with less pericardial constraint, anti-fibrotic effects, and a metabolic shift toward more oxygen-efficient ketone (beta-hydroxybutyrate) oxidation.

Option A: Option A is incorrect because the class is not a direct positive inotrope and benefit does not depend on raising ejection fraction.
Option B: Option B is incorrect because SGLT-2 inhibitors do not act by lowering low-density lipoprotein or regressing plaque, which would not reverse diastolic dysfunction.
Option C: Option C is incorrect because potent direct coronary vasodilation independent of loading is not the proposed mechanism.
Option D: Option D is incorrect because the class produces its volume effects without strong neurohormonal activation and does not work by augmenting contractility.

12. [CASE 3 — QUESTION 4] Continuing with the same patient. E.T. is also started on an angiotensin receptor blocker for her albuminuric chronic kidney disease, and the team plans to continue empagliflozin. What is the best integrated rationale for using both agents for renal protection?

A) The two are redundant because both reduce intraglomerular pressure by acting on the efferent arteriole
B) The combination should be avoided because constricting one arteriole and dilating the other cancels the renal benefit
C) The two agents reduce intraglomerular pressure at different nodes: the angiotensin receptor blocker dilates the efferent arteriole while empagliflozin constricts the afferent arteriole via tubuloglomerular feedback, so their renoprotective effects are complementary rather than redundant
D) Empagliflozin protects the kidney only by improving glycemic control, so in a non-diabetic patient it adds nothing to the angiotensin receptor blocker
E) The angiotensin receptor blocker constricts the afferent arteriole and empagliflozin dilates the efferent arteriole, so together they raise filtration fraction

ANSWER: C

Rationale:

The angiotensin receptor blocker (a renin-angiotensin-aldosterone system blocker) reduces intraglomerular pressure chiefly by dilating the efferent arteriole, whereas empagliflozin reduces it by constricting the afferent arteriole through tubuloglomerular feedback. Because they act on different nodes of the glomerular circuit, their renoprotective effects are complementary and additive.

Option A: Option A is incorrect because the agents do not both act on the efferent arteriole and are not redundant.
Option B: Option B is incorrect because acting on different arterioles does not cancel benefit; both lower intraglomerular pressure.
Option D: Option D is incorrect because empagliflozin's renoprotection is largely hemodynamic and independent of glycemic improvement, so it adds benefit even without diabetes.
Option E: Option E is incorrect because it inverts both mechanisms and wrongly implies a rise in filtration fraction; the combination lowers intraglomerular pressure.

13. [CASE 4 — QUESTION 1] A 59-year-old man (D.P.) with type 2 diabetes mellitus on dapagliflozin is scheduled for an elective open abdominal hernia repair in one week. The preoperative clinic is establishing his medication plan. What is the correct perioperative instruction for the dapagliflozin?

A) Stop dapagliflozin 3 to 4 days before the planned surgery to reduce the risk of perioperative euglycemic diabetic ketoacidosis
B) Continue dapagliflozin through the morning of surgery to prevent perioperative hyperglycemia
C) Continue dapagliflozin and double the dose during the fasting period to maintain glycemic control
D) Stop dapagliflozin only on the morning of surgery, which provides adequate washout
E) Make no change, because a normal preoperative glucose guarantees there is no perioperative metabolic risk

ANSWER: A

Rationale:

Because SGLT-2 inhibitors predispose to perioperative euglycemic diabetic ketoacidosis during fasting and surgical stress, the established protocol is to stop the drug 3 to 4 days before planned major surgery.

Option B: Option B is incorrect because continuing through the morning of surgery leaves the patient exposed to perioperative euglycemic ketoacidosis.
Option C: Option C is incorrect because increasing the dose during the fasting period raises the risk of euglycemic ketoacidosis.
Option D: Option D is incorrect because a single morning-of hold does not provide adequate washout given the drug's pharmacodynamic persistence; a 3-to-4-day interval is needed.
Option E: Option E is incorrect because a normal preoperative glucose does not exclude euglycemic ketoacidosis, so it cannot justify making no change.

14. [CASE 4 — QUESTION 2] Continuing with the same patient. D.P.'s surgery is unexpectedly moved up and he took his dapagliflozin two days ago. On arrival his point-of-care glucose is normal, and the anesthesia team is reassured. Integrating the euglycemic ketoacidosis mechanism, what is the correct interpretation?

A) A normal glucose confirms there is no metabolic risk, so the case can proceed without any additional testing
B) A normal glucose means euglycemic ketoacidosis is impossible, since that entity always presents with markedly elevated glucose
C) The dapagliflozin should be redosed preoperatively to ensure stable glucose during the procedure
D) A normal glucose is falsely reassuring because euglycemic diabetic ketoacidosis can occur with near-normal glucose; ketones should be checked given his recent dose, and a proper preoperative plan would have held the drug 3 to 4 days in advance rather than relying on the glucose value
E) The glucose is irrelevant and the recent dose poses no concern, so no ketone testing is warranted

ANSWER: D

Rationale:

Because euglycemic diabetic ketoacidosis can occur with near-normal glucose, a normal preoperative glucose is falsely reassuring; given D.P. took dapagliflozin two days ago, ketones should be checked, and the correct preoperative plan would have held the drug 3 to 4 days in advance rather than relying on the glucose value.

Option A: Option A is incorrect because a normal glucose does not confirm the absence of metabolic risk in this setting.
Option B: Option B is incorrect because euglycemic ketoacidosis specifically occurs without markedly elevated glucose, so a normal glucose does not exclude it.
Option C: Option C is incorrect because redosing the drug perioperatively increases, rather than reduces, ketoacidosis risk.
Option E: Option E is incorrect because the recent dose does pose concern, and ketone testing is warranted rather than dismissed.

15. [CASE 4 — QUESTION 3] Continuing with the same patient. D.P. undergoes surgery uneventfully and is recovering on the ward. The team asks when his dapagliflozin may be safely resumed. Which set of criteria is correct?

A) Resume immediately in the post-anesthesia care unit regardless of oral intake, to avoid postoperative hyperglycemia
B) Resume only after he is eating and drinking normally, has negative ketones, and has no ongoing infection or acute illness
C) Resume on postoperative day one automatically, irrespective of intake, ketones, or infection status
D) Do not resume dapagliflozin for at least three months after any surgery as a fixed rule
E) Resume at a tripled dose to make up for the perioperative period during which it was held

ANSWER: B

Rationale:

After surgery, an SGLT-2 inhibitor should be resumed only once the patient is eating and drinking normally, has negative ketones, and has no ongoing infection or acute illness, mirroring the sick-day resumption logic.

Option A: Option A is incorrect because resuming before normal oral intake risks recurrent euglycemic ketoacidosis.
Option C: Option C is incorrect because automatic resumption on a fixed postoperative day, irrespective of intake and ketones, ignores the relevant safety criteria.
Option D: Option D is incorrect because a fixed three-month prohibition is not the standard; resumption depends on the clinical criteria, not an arbitrary interval.
Option E: Option E is incorrect because tripling the dose is inappropriate and would increase the risk of recurrence.

16. [CASE 4 — QUESTION 4] Continuing with the same patient. Months later, D.P. requires emergency surgery for appendicitis and there is no time for a multi-day drug hold; he last took dapagliflozin yesterday. What is the most appropriate perioperative metabolic precaution?

A) Proceed without checking ketones, since the glucose is normal and there is no time for testing
B) Cancel the emergency surgery until a 3-to-4-day dapagliflozin washout can be completed
C) Check ketones (and a blood gas) regardless of the plasma glucose level, and monitor closely perioperatively for euglycemic diabetic ketoacidosis, since a multi-day hold was not possible
D) Administer a preoperative dose of dapagliflozin to stabilize glucose before the procedure
E) Rely on the normal glucose alone to exclude euglycemic ketoacidosis throughout the perioperative course

ANSWER: C

Rationale:

When emergency surgery does not allow the recommended multi-day hold, the appropriate precaution is to check ketones and a blood gas regardless of the plasma glucose level and monitor closely for euglycemic diabetic ketoacidosis perioperatively, because the recent dose leaves the patient at risk.

Option A: Option A is incorrect because a normal glucose does not exclude euglycemic ketoacidosis, so ketones should be checked.
Option B: Option B is incorrect because emergency surgery for appendicitis should not be delayed for a multi-day drug washout.
Option D: Option D is incorrect because giving another dose preoperatively increases ketoacidosis risk.
Option E: Option E is incorrect because relying on a normal glucose alone fails to detect euglycemic ketoacidosis, which can occur without hyperglycemia.

17. [CASE 5 — QUESTION 1] A 67-year-old man (A.S.) with type 2 diabetes mellitus has established atherosclerotic cardiovascular disease (prior myocardial infarction) and heart failure with reduced ejection fraction. He is on metformin with an HbA1c of 8.1%, and his clinician wants add-on therapy that addresses both his atherosclerotic and heart failure risks. Which strategy is best supported?

A) Add a sulfonylurea, which provides both atherosclerotic and heart failure outcome benefit
B) Add a dipeptidyl peptidase-4 inhibitor, which reduces both myocardial infarction and heart failure hospitalization
C) Add a thiazolidinedione, which is preferred in heart failure with reduced ejection fraction and reduces atherosclerotic events
D) Add a second SGLT-2 inhibitor on top of a first to cover both atherosclerotic and heart failure risk through additive glycosuria
E) Add an SGLT-2 inhibitor for heart failure benefit and a glucagon-like peptide-1 receptor agonist for atherosclerotic risk reduction, since the two classes address complementary cardiovascular pathways and can be combined

ANSWER: E

Rationale:

A.S. has both established atherosclerotic disease and heart failure. An SGLT-2 inhibitor addresses heart failure risk through its hemodynamic, heart-failure-oriented benefit, while a glucagon-like peptide-1 receptor agonist addresses atherosclerotic risk; the two classes target complementary pathways and can be combined.

Option A: Option A is incorrect because sulfonylureas lack proven atherosclerotic or heart failure outcome benefit.
Option B: Option B is incorrect because dipeptidyl peptidase-4 inhibitors do not reduce myocardial infarction, and some raise heart failure hospitalization concerns rather than reducing it.
Option C: Option C is incorrect because thiazolidinediones cause fluid retention and are contraindicated in symptomatic heart failure with reduced ejection fraction.
Option D: Option D is incorrect because two SGLT-2 inhibitors should never be combined and would not address the atherosclerotic component.

18. [CASE 5 — QUESTION 2] Continuing with the same patient. A.S. is started on empagliflozin and a glucagon-like peptide-1 receptor agonist, and his basal insulin is about to be added for glycemic control. Which combination and dosing principle is correct?

A) Do not combine two SGLT-2 inhibitors with each other; when adding empagliflozin (and basal insulin) to the regimen, reduce the basal insulin by roughly 20% at initiation to limit hypoglycemia from the added glucose-lowering effect
B) Add a second SGLT-2 inhibitor alongside empagliflozin for additive glycosuria, and increase the basal insulin at initiation
C) Combine two SGLT-2 inhibitors and leave insulin unchanged, since SGLT-2 inhibitors carry no hypoglycemia risk in any combination
D) Stop the glucagon-like peptide-1 receptor agonist because it cannot be combined with an SGLT-2 inhibitor
E) Triple the empagliflozin dose when insulin is added, to overcome insulin-related resistance

ANSWER: A

Rationale:

Two SGLT-2 inhibitors should never be combined. When an SGLT-2 inhibitor is added to insulin, the insulin dose is typically reduced by about 20% at initiation to limit hypoglycemia from the added glucose-lowering effect; the SGLT-2 inhibitor and glucagon-like peptide-1 receptor agonist are a complementary, appropriate pairing.

Option B: Option B is incorrect because two SGLT-2 inhibitors should not be combined and insulin should be reduced, not increased.
Option C: Option C is incorrect because two SGLT-2 inhibitors should not be combined, and with concurrent insulin there is a real hypoglycemia risk to manage.
Option D: Option D is incorrect because the glucagon-like peptide-1 receptor agonist and SGLT-2 inhibitor are appropriately combined.
Option E: Option E is incorrect because the SGLT-2 inhibitor dose is not tripled with insulin; the relevant adjustment is a reduction in the insulin dose.

19. [CASE 5 — QUESTION 3] Continuing with the same patient. Six weeks into empagliflozin therapy, A.S. (an uncircumcised man) develops a first episode of balanitis with itching and erythema of the glans. He is otherwise well and benefiting from therapy. What is the most appropriate management?

A) Permanently discontinue empagliflozin, since a single genital infection is an absolute contraindication to the class
B) Switch him to insulin monotherapy, since a genital mycotic infection indicates failure of SGLT-2 inhibitor therapy
C) Withhold antifungal treatment and lower the empagliflozin dose instead, since treating the infection while continuing the drug is unsafe
D) Treat the balanitis with a standard topical or oral antifungal and continue empagliflozin with hygiene counseling, since genital mycotic infections are the most common adverse effect of the class, are usually mild to moderate, and do not require discontinuation unless recurrent or severe
E) Begin indefinite chronic systemic antifungal prophylaxis for the duration of empagliflozin therapy

ANSWER: D

Rationale:

Genital mycotic infections (such as balanitis in uncircumcised men) are the most common adverse effect of SGLT-2 inhibitors, arising from glucosuria favoring Candida growth. They are usually mild to moderate, respond to standard topical or oral antifungal therapy, and do not require drug discontinuation unless recurrent or severe; continuing the drug with hygiene counseling is appropriate for a first, uncomplicated episode.

Option A: Option A is incorrect because a single episode is not an absolute contraindication.
Option B: Option B is incorrect because a mycotic infection does not indicate therapeutic failure and does not warrant switching to insulin monotherapy.
Option C: Option C is incorrect because the infection should be treated, and continuing the drug during treatment is acceptable.
Option E: Option E is incorrect because indefinite chronic systemic antifungal prophylaxis is not indicated for all patients on the class.

20. [CASE 5 — QUESTION 4] Continuing with the same patient. A.S. is now 80 years old with a blood pressure of 106/64 mmHg, taking furosemide and an angiotensin-converting enzyme inhibitor, and the team is restarting empagliflozin after a hospitalization. What initiation strategy best accounts for his volume status?

A) Start at the maximum dose and add another antihypertensive simultaneously, since there is no volume-related risk in this combination
B) Anticipate additive volume depletion and initiate at a lower dose with blood pressure monitoring, considering a reduction in the furosemide dose, because the osmotic diuresis and natriuresis of empagliflozin compound the volume loss from the loop diuretic and the blood-pressure lowering of the angiotensin-converting enzyme inhibitor, a risk amplified in an elderly patient with low baseline blood pressure
C) Increase the furosemide dose at the same time, to counteract the fluid retention empagliflozin will cause
D) Discontinue the angiotensin-converting enzyme inhibitor, since it cannot be used with an SGLT-2 inhibitor
E) Make no adjustments and avoid monitoring, since empagliflozin raises blood pressure and will offset the other agents

ANSWER: B

Rationale:

In an elderly patient with low-normal blood pressure on a loop diuretic and a renin-angiotensin blocker, the osmotic diuresis and natriuresis of empagliflozin add to existing volume depletion and blood-pressure lowering. The appropriate strategy is to initiate at a lower dose with blood pressure monitoring and consider reducing the concurrent loop diuretic.

Option A: Option A is incorrect because starting at maximum dose and adding another antihypertensive ignores the additive volume risk.
Option C: Option C is incorrect because empagliflozin causes volume loss, not retention, so increasing the loop diuretic would worsen depletion.
Option D: Option D is incorrect because SGLT-2 inhibitors and renin-angiotensin blockers are appropriately used together, especially in heart failure.
Option E: Option E is incorrect because empagliflozin modestly lowers, not raises, blood pressure, so it adds to rather than offsets the hypotensive risk, and monitoring is warranted.

21. [CASE 6 — QUESTION 1] A 61-year-old man (G.W.) with type 2 diabetes mellitus on an SGLT-2 inhibitor presents with 24 hours of rapidly worsening perineal pain, swelling, and erythema extending toward the scrotum, accompanied by fever, tachycardia, and pain out of proportion to the visible findings. What is the most appropriate immediate management?

A) Prescribe an outpatient oral antifungal and arrange follow-up in two weeks
B) Continue the SGLT-2 inhibitor and apply a topical antibiotic to the affected area
C) Reduce the SGLT-2 inhibitor dose and observe for 48 hours before further action
D) Reassure and discharge him, since perineal symptoms in patients on this class are uniformly benign
E) Discontinue the SGLT-2 inhibitor and obtain emergent surgical consultation for suspected Fournier gangrene, while initiating broad-spectrum antibiotics and resuscitation, because early surgical debridement is critical to survival

ANSWER: E

Rationale:

Rapidly progressive perineal pain, swelling, and erythema with systemic toxicity and pain out of proportion in a patient on an SGLT-2 inhibitor is concerning for Fournier gangrene, a life-threatening necrotizing fasciitis of the perineum and genitalia. Management requires discontinuing the drug, obtaining emergent surgical consultation, and initiating broad-spectrum antibiotics and resuscitation, because early surgical debridement is critical to survival.

Option A: Option A is incorrect because outpatient antifungal therapy dangerously delays surgical care of a necrotizing infection.
Option B: Option B is incorrect because continuing the drug and applying a topical antibiotic fails to address a surgical emergency.
Option C: Option C is incorrect because dose reduction and 48-hour observation delay definitive treatment of a fulminant infection.
Option D: Option D is incorrect because these symptoms are not benign; they represent a surgical emergency.

22. [CASE 6 — QUESTION 2] Continuing with the same patient. After recovery and reassessment, G.W. is later restarted on an SGLT-2 inhibitor and is then prescribed a strong cytochrome P450 3A4 (CYP3A4) inhibitor for an unrelated condition. Based on the metabolism of the SGLT-2 inhibitor class, what interaction is expected?

A) A large rise in SGLT-2 inhibitor exposure, because the class is predominantly metabolized by CYP3A4 and its clearance will fall sharply
B) Loss of SGLT-2 inhibitor efficacy, because CYP3A4 is required to convert these agents from inactive prodrugs to active drug
C) Minimal CYP-mediated interaction, because SGLT-2 inhibitors are metabolized primarily by glucuronidation (UDP-glucuronosyltransferase enzymes) with only minimal cytochrome P450 involvement
D) A sharp rise in renal clearance of the SGLT-2 inhibitor, because CYP3A4 inhibition upregulates tubular secretion of glucuronides
E) Dangerous accumulation, because SGLT-2 inhibitors are eliminated entirely unchanged by the kidney and CYP3A4 inhibition blocks their only elimination route

ANSWER: C

Rationale:

The SGLT-2 inhibitor class is metabolized primarily by glucuronidation through UDP-glucuronosyltransferase (UGT) enzymes, with only minimal cytochrome P450 (CYP450) involvement, so a strong CYP3A4 inhibitor is expected to produce minimal clinically significant change in exposure.

Option A: Option A is incorrect because the class is not predominantly CYP3A4-metabolized, so a large CYP-mediated exposure increase is not expected.
Option B: Option B is incorrect because these agents are active drugs, not CYP3A4-dependent prodrugs, so CYP inhibition does not abolish efficacy.
Option D: Option D is incorrect because CYP3A4 inhibition does not upregulate tubular secretion of glucuronides, and renal clearance would not rise on this basis.
Option E: Option E is incorrect because the agents are cleared substantially by glucuronidation rather than entirely unchanged by the kidney, and CYP3A4 is not their elimination route.

23. [CASE 6 — QUESTION 3] Continuing with the same patient. While selecting a specific agent for G.W., the team reviews SGLT-2 versus SGLT-1 selectivity across the class. Which statement is correct?

A) Empagliflozin is the most SGLT-2 selective agent with negligible SGLT-1 activity, whereas canagliflozin has partial SGLT-1 inhibitory activity that is modest at 100 mg and more pronounced at the 300 mg dose
B) Canagliflozin is the most SGLT-2 selective agent, while empagliflozin has the greatest SGLT-1 cross-reactivity of the class
C) Dapagliflozin has substantial intestinal SGLT-1 activity at standard doses, which accounts for diarrhea that distinguishes it from the rest of the class
D) All four agents share identical SGLT-2/SGLT-1 selectivity, so selectivity is not a distinguishing feature
E) Ertugliflozin is the least selective agent and derives most of its glycosuric effect from intestinal SGLT-1 blockade

ANSWER: A

Rationale:

Empagliflozin is the most SGLT-2 selective agent in the class with negligible SGLT-1 activity, and dapagliflozin is also highly selective; canagliflozin has lower selectivity, with partial SGLT-1 inhibitory activity that is modest at 100 mg and more pronounced at 300 mg.

Option B: Option B is incorrect because it reverses the relationship: canagliflozin, not empagliflozin, has the SGLT-1 cross-activity, and empagliflozin is the most selective.
Option C: Option C is incorrect because dapagliflozin is highly SGLT-2 selective with minimal SGLT-1 activity; canagliflozin is the agent with appreciable SGLT-1 activity.
Option D: Option D is incorrect because selectivity differs meaningfully across agents.
Option E: Option E is incorrect because ertugliflozin does not derive its effect chiefly from intestinal SGLT-1 blockade; the class mechanism is renal SGLT-2 inhibition.

24. [CASE 6 — QUESTION 4] Continuing with the same patient's care team. A different patient on the unit, a 29-year-old woman with type 1 diabetes mellitus, was placed on an SGLT-2 inhibitor off-label as an insulin adjunct and now presents with nausea, vomiting, Kussmaul respirations, a glucose of 205 mg/dL, a high anion-gap metabolic acidosis, and elevated beta-hydroxybutyrate. Which statement best captures the issue?

A) The near-normal glucose of 205 mg/dL excludes ketoacidosis, so another diagnosis should be pursued
B) SGLT-2 inhibitors are FDA-approved in type 1 diabetes mellitus, so this complication is unexpected and unrelated to the drug
C) This is a hyperosmolar hyperglycemic state, the characteristic SGLT-2 inhibitor complication in type 1 diabetes mellitus
D) This is euglycemic diabetic ketoacidosis: SGLT-2 inhibitors markedly increase ketoacidosis risk in type 1 diabetes mellitus (where they are not FDA-approved), so the drug should be discontinued and she should be treated for ketoacidosis with insulin, fluids, and glucose as needed
E) The SGLT-2 inhibitor should be continued and her insulin reduced, since the acidosis reflects insulin excess rather than ketoacidosis

ANSWER: D

Rationale:

This is euglycemic diabetic ketoacidosis. SGLT-2 inhibitors markedly increase ketoacidosis risk in type 1 diabetes mellitus, where they are not FDA-approved, because relative insulin deficiency drives ketogenesis while glycosuria keeps glucose only modestly elevated. The drug should be discontinued and the ketoacidosis treated with insulin, fluids, and glucose as needed.

Option A: Option A is incorrect because a glucose of 205 mg/dL with a high anion-gap acidosis and elevated beta-hydroxybutyrate is diagnostic of euglycemic ketoacidosis, not a reason to exclude it.
Option B: Option B is incorrect because SGLT-2 inhibitors are not FDA-approved in type 1 diabetes mellitus, and this complication is a recognized risk of such off-label use.
Option C: Option C is incorrect because the picture is a ketoacidosis with elevated ketones, not a hyperosmolar hyperglycemic state.
Option E: Option E is incorrect because the acidosis is a ketoacidosis driven by ketogenesis, not insulin excess, and continuing the drug while reducing insulin would worsen it.