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PEBC Pharmacist Evaluating Examination

4.2 Cardiovascular, Renal, and Endocrine Pharmacology

Q: A 62-year-old patient with Heart Failure with Reduced Ejection Fraction (HFrEF, LVEF 28%) is being optimized on guideline-directed medical therapy. The cardiologist prescribes sacubitril/valsartan to replace ramipril 10 mg daily. Which instruction regarding the transition is critical to prevent a life-threatening adverse reaction?

A mandatory 36-hour washout period must elapse between the last dose of ramipril and the first dose of sacubitril/valsartan.. Both angiotensin-converting enzyme (ACE) inhibitors and neprilysin degrade bradykinin. Co-administering an ACE inhibitor (such as ramipril) with a neprilysin inhibitor (sacubitril) leads to massive synergistic accumulation of bradykinin, which precipitates severe, potentially fatal angioedema. Health Canada and clinical practice guidelines strictly require a mandatory 36-hour washout period between discontinuing an ACE inhibitor and initiating sacubitril/valsartan. In contrast, transitioning from an ARB to sacubitril/valsartan does not require a 36-hour washout period because ARBs do not inhibit bradykinin degradation. Immediate switching or overlapping dual therapy is strictly contraindicated due to angioedema risk. Sacubitril is not approved or available as monotherapy, as inhibiting neprilysin alone causes compensatory renin-angiotensin activation.

Q: A 54-year-old patient with type 2 diabetes managed on metformin and empagliflozin presents to the emergency department with nausea, vomiting, tachypnea, and severe fatigue 48 hours following elective laparoscopic cholecystectomy. Laboratory analysis demonstrates an arterial pH of 7.22, serum bicarbonate of 11 mmol/L, serum beta-hydroxybutyrate of 4.8 mmol/L, and a blood glucose of 8.2 mmol/L. What physiological mechanism explains this patient's clinical state?

SGLT2 inhibitors induce glucosuria and decrease circulating insulin while increasing glucagon, promoting hepatic ketogenesis even with near-normal blood glucose levels.. This patient is presenting with euglycemic diabetic ketoacidosis (euDKA), a known complication of SGLT2 inhibitor therapy (empagliflozin) triggered by physiological stressors such as surgery, fasting, or acute infection. SGLT2 inhibitors promote persistent urinary glucose excretion, which lowers circulating blood glucose levels and reduces endogenous pancreatic insulin secretion while concurrently stimulating glucagon secretion. The reduced insulin-to-glucagon ratio triggers accelerated lipolysis and uninhibited hepatic free fatty acid oxidation, generating high concentrations of ketone bodies (beta-hydroxybutyrate, acetoacetate). Because persistent renal glucosuria keeps plasma glucose levels near-normal (<14 mmol/L), diagnosis is often dangerously delayed. SGLT2 inhibitors do not stimulate alpha-cell insulin secretion, do not inhibit mitochondrial beta-oxidation, and do not directly block renal ketone clearance.

Q: A 68-year-old patient with hypertension is prescribed chlorthalidone 25 mg daily. Compared to loop diuretics such as furosemide, which metabolic and electrolyte pattern is uniquely characteristic of thiazide and thiazide-like diuretics?

Hypokalemic metabolic alkalosis combined with hypercalcemia and hyponatremia. Thiazide and thiazide-like diuretics (such as chlorthalidone and hydrochlorothiazide) inhibit the Na+/Cl- (NCCT) cotransporter in the distal convoluted tubule. This increases luminal sodium delivery to the cortical collecting duct, promoting potassium and hydrogen ion excretion, leading to hypokalemic metabolic alkalosis. In the distal tubule, reduced intracellular sodium enhances basolateral Na+/Ca2+ antiporter activity, stimulating active transcellular calcium reabsorption and producing hypercalcemia (unlike loop diuretics, which cause hypocalcemia through calcium wasting). Thiazides also frequently cause hyponatremia by impairing urinary diluting capacity in the cortical nephron without affecting the medullary concentrating gradient. Thiazides cause hypokalemia rather than hyperkalemia, and they promote calcium retention rather than wasting.

Q: A 28-year-old woman in her sixth week of pregnancy is diagnosed with severe Graves' disease thyrotoxicosis. Which statement accurately reflects Canadian clinical guidelines regarding thionamide antithyroid drug selection and safety monitoring?

Propylthiouracil is preferred during the first trimester of pregnancy and in thyroid storm, but carries a higher risk of fulminant hepatotoxicity compared to methimazole.. Propylthiouracil (PTU) is the preferred antithyroid agent during the first trimester of pregnancy because methimazole exposure during organogenesis (weeks 6-10) is associated with characteristic teratogenic embryopathy (aplasia cutis congenita, choanal atresia, tracheoesophageal fistula). PTU is also preferred in acute thyroid storm because, in addition to inhibiting thyroid peroxidase (TPO), it uniquely inhibits peripheral 5'-deiodinase, blocking the conversion of T4 to active T3. However, PTU carries a boxed warning for severe, unpredictable fulminant hepatic necrosis, making methimazole the preferred agent outside of the first trimester and thyroid storm. Both agents carry a similar risk of rare, life-threatening agranulocytosis (~0.2-0.5%), which mandates immediate complete blood count testing if fever or sore throat develops.

Key Takeaways

Inhibition of the renin-angiotensin-aldosterone system with ACE inhibitors, ARBs, or ARNIs reduces cardiovascular and renal morbidity; switching from an ACE inhibitor to sacubitril/valsartan requires a mandatory 36-hour washout to prevent life-threatening angioedema.
Dihydropyridine calcium channel blockers selectively dilate peripheral arterioles, whereas non-dihydropyridines (diltiazem, verapamil) exert negative chronotropic, dromotropic, and inotropic effects and are potent CYP3A4 inhibitors contraindicated in HFrEF.
Loop diuretics (furosemide) block NKCC2 cotransporters in the thick ascending limb, causing calcium and magnesium wasting, whereas thiazides block NCCT cotransporters in the distal convoluted tubule and promote calcium retention.
Diabetes Canada guidelines recommend SGLT2 inhibitors and GLP-1 receptor agonists with proven cardiorenal benefit for patients with type 2 diabetes and atherosclerotic cardiovascular disease, heart failure, or chronic kidney disease.
Thionamide antithyroid therapy requires vigilantly monitoring for agranulocytosis; propylthiouracil (PTU) is preferred in the first trimester of pregnancy and thyroid storm due to peripheral T4-to-T3 conversion blockade, but carries higher fulminant hepatotoxicity risks compared to methimazole.

Last updated: August 2026

4.2 Cardiovascular, Renal, and Endocrine Pharmacology

Cardiovascular, renal, and metabolic disorders represent the highest-volume pharmacotherapeutic encounters in Canadian institutional and community pharmacy practice. Understanding molecular mechanisms, hemodynamic cascades, Canadian clinical practice guidelines (Hypertension Canada, CCS Heart Failure, Diabetes Canada), and toxicities is essential for candidate success on the PEBC Evaluating Examination.

1. Renin-Angiotensin-Aldosterone System (RAAS) and Vasodilator Pharmacology

+--------------------------------------------------------------------------------------+
|                   RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM CASCADE                       |
+--------------------------------------------------------------------------------------+
|  [Angiotensinogen] (Liver)
|         |
|         v <--- Renin (Juxtaglomerular Cells: stimulated by low perfusion / beta-1)
|  [Angiotensin I]
|         |
|         v <--- ACE / Kininase II (Inhibited by ACE Inhibitors) ===[X] Bradykinin Breakdown
|  [Angiotensin II]                                                  (Cough / Angioedema)
|         |
|         +---> AT1 Receptor (Blocked by ARBs) ---> Vasoconstriction + Aldosterone Release
|         +---> AT2 Receptor ---> Vasodilation + Antiproliferation
|                                                                                      |
|  [Natriuretic Peptides: ANP, BNP] ===> Vasodilation + Natriuresis                   |
|         |
|         v <--- Neprilysin (Inhibited by Sacubitril)                                 |
|  [Inactive Fragments]                                                               |
+--------------------------------------------------------------------------------------+

RAAS Inhibitor Classes and Clinical Mechanics

Angiotensin-Converting Enzyme (ACE) Inhibitors (Ramipril, Perindopril, Enalapril): Inhibit ACE, preventing conversion of Ang I to Ang II, dilating the renal efferent arteriole (reducing intraglomerular pressure and proteinuria), and reducing systemic vascular resistance. Concurrently block kininase II, causing bradykinin accumulation, which mediates dry cough ( $10-20\%$ ) and rare, life-threatening angioedema.
Angiotensin Receptor Blockers (ARBs: Candesartan, Valsartan, Telmisartan): Competitive antagonists at the $\text{AT}_1$ receptor. Provide equivalent blood pressure lowering and nephroprotection without increasing bradykinin, resulting in minimal cough or angioedema risk.
Angiotensin Receptor-Neprilysin Inhibitors (ARNI: Sacubitril/Valsartan): Sacubitril prodrug inhibits neprilysin, elevating circulating natriuretic peptides (ANP, BNP, CNP), bradykinin, and adrenomedullin. Valsartan blocks $\text{AT}_1$ $AT_{1}$ receptors. Indicated for Heart Failure with Reduced Ejection Fraction (HFrEF, CCS guidelines).
- Mandatory Safety Mandate: A 36-hour washout period is legally and clinically required when transitioning a patient from an ACE inhibitor to sacubitril/valsartan. Simultaneous neprilysin and ACE inhibition produces massive bradykinin surges and severe angioedema.
Mineralocorticoid Receptor Antagonists (MRAs):
- Spironolactone: Non-selective MRA; also blocks androgen and progesterone receptors, predisposing to gynecomastia, breast tenderness, and menstrual irregularities.
- Eplerenone: Highly selective MRA with minimal endocrine side effects.
- Finerenone: Non-steroidal, selective MRA authorized to slow CKD progression and reduce cardiovascular events in type 2 diabetes.
- Electrolyte Hazard: All MRAs cause hyperkalemia; potassium and serum creatinine must be monitored within $1-2\text{ weeks}$ of initiation.

Vasodilators: Calcium Channel Blockers and Nitrates

Drug Class	Representative Agents	Mechanism of Action	Hemodynamic / Clinical Effects	Adverse Effects & Pearls
Dihydropyridine CCBs	Amlodipine, Nifedipine XL, Felodipine	Selective block of vascular L-type $\text{Ca}^{2+}$ channels ( $\text{Ca}_v1.2$ )	Arteriolar vasodilation, $\downarrow$ SVR, no intrinsic negative inotropy	Peripheral dependent ankle edema (precapillary dilation), reflex tachycardia, flushing, headache
Non-Dihydropyridine CCBs	Diltiazem, Verapamil	Block L-type $\text{Ca}^{2+}$ channels in myocardium, SA node, and AV node	Negative chronotropy, negative dromotropy, negative inotropy	Bradycardia, AV block, constipation (verapamil relaxes colonic smooth muscle). Potent CYP3A4 and P-gp inhibitors. Contraindicated in HFrEF (LVEF $<40\%$ )
Organic Nitrates	Nitroglycerin, Isosorbide dinitrate/mononitrate	Bioactivated by mitochondrial ALDH-2 to release NO $\to \uparrow$ cGMP	Predominant venodilation $\to \downarrow$ preload, $\downarrow$ wall stress; coronary vasodilation	Nitrate tolerance avoided via daily $10-12\text{ hour}$ nitrate-free interval. Co-administration with PDE-5 inhibitors (sildenafil, tadalafil) is strictly contraindicated (fatal refractory hypotension)

2. Renal Pharmacology and Diuretic Mechanisms

Diuretics modulate renal tubular electrolyte transporters, altering sodium excretion, intravascular volume, and systemic hemodynamics.

+--------------------------------------------------------------------------------------+
|                     RENAL TUBULAR SITES OF DIURETIC ACTION                           |
+--------------------------------------------------------------------------------------+
|  1. Proximal Convoluted Tubule: Carbonic Anhydrase Inhibitors (Acetazolamide)        |
|     - Blocks NaHCO3 reabsorption -> alkaline diuresis, metabolic acidosis            |
|  2. Thick Ascending Limb Loop : Loop Diuretics (Furosemide, Bumetanide)              |
|     - Blocks NKCC2 cotransporter -> Ca2+ and Mg2+ wasting; abolishes medullary grad  |
|  3. Distal Convoluted Tubule  : Thiazides (Hydrochlorothiazide, Chlorthalidone)      |
|     - Blocks NCCT cotransporter -> Ca2+ retention; ineffective if eGFR <30           |
|  4. Cortical Collecting Duct  : K+-Sparing Diuretics (Amiloride, Spironolactone)     |
|     - Blocks ENaC / Aldosterone -> K+ retention, metabolic acidosis                  |
+--------------------------------------------------------------------------------------+

Diuretic Comparison Matrix

Loop Diuretics (Furosemide, Bumetanide, Torsemide): Inhibit the luminal $\text{Na}^+/\text{K}^+/2\text{Cl}^-$ (NKCC2) symporter in the thick ascending limb of the loop of Henle. Abolish the hypertonic medullary interstitial gradient, providing potent natriuresis and diuresis. Promote urinary wasting of $\text{Na}^+, \text{K}^+, \text{Cl}^-, \text{Mg}^{2+}$ , and $\text{Ca}^{2+}$ (used acutely in hypercalcemia). Adverse effects: Hypokalemic metabolic alkalosis, hypocalcemia, hypomagnesemia, hyperuricemia, and ototoxicity (dose-dependent, synergistic with aminoglycosides).
Thiazide and Thiazide-Like Diuretics (Hydrochlorothiazide, Chlorthalidone, Indapamide, Metolazone): Inhibit the $\text{Na}^+/\text{Cl}^-$ (NCCT) cotransporter in the distal convoluted tubule. Promote calcium reabsorption via basolateral $\text{Na}^+/\text{Ca}^{2+}$ exchange (beneficial in osteopenia/osteoporosis and calcium nephrolithiasis). Adverse effects: Hypokalemia, hyponatremia, hypercalcemia, hyperuricemia (precipitating gout), and hyperglycemia. Ineffective as monotherapy when $\text{eGFR} < 30\text{ mL/min/1.73 m}^2$ (except indapamide and metolazone).
Potassium-Sparing Diuretics (Amiloride, Triamterene): Directly block Epithelial Sodium Channels (ENaC) in principal cells of the late distal tubule and cortical collecting duct, preventing $\text{Na}^+$ reabsorption and decreasing the lumen-negative transepithelial potential that drives $\text{K}^+$ and $\text{H}^+$ secretion.

3. Antiarrhythmic Pharmacology (Vaughan Williams Classification)

Antiarrhythmic drugs modify cardiac ion channels and action potential dynamics:

+--------------------------------------------------------------------------------------+
|                 VAUGHAN WILLIAMS ANTIARRHYTHMIC CLASSIFICATION                       |
+--------------------------------------------------------------------------------------+
|  Class Ia : Moderate Na+ block + K+ block (Procainamide, Quinidine, Disopyramide)    |
|             -> Prolongs QRS and APD / QT; intermediate dissociation kinetics         |
|  Class Ib : Fast Na+ block (Lidocaine, Mexiletine)                                   |
|             -> Shortens APD; binds ischemic/depolarized tissue; zero QT prolongation |
|  Class Ic : Potent Na+ block (Flecainide, Propafenone)                               |
|             -> Marked QRS widening, no effect on APD; contraindicated post-MI (CAST) |
|  Class II : Beta-Adrenoceptor Antagonists (Metoprolol, Bisoprolol, Esmolol)          |
|  Class III: K+ Channel Blockers (Amiodarone, Dronedarone, Sotalol)                   |
|             -> Prolongs APD / QT; Torsades de Pointes risk (low with amiodarone)     |
|  Class IV : Non-Dihydropyridine CCBs (Verapamil, Diltiazem)                          |
|  Class V  : Adenosine (A1 agonist, converts PSVT), Digoxin, Ivabradine (If blocker)  |
+--------------------------------------------------------------------------------------+

Flecainide and Propafenone (Class Ic): Exhibit slow dissociation kinetics from open $\text{Na}^+$ channels. In the Cardiac Arrhythmia Suppression Trial (CAST), Class Ic agents increased mortality in patients with prior myocardial infarction or structural heart disease; they are strictly contraindicated in structural/ischemic heart disease.
Amiodarone (Class III): Exhibits Class I, II, III, and IV actions. Contains iodine ( $37\%$ $37%$ by weight) and has a prolonged elimination half-life ( $t_{1/2} \approx 40-60\text{ days}$ $t_{1/2} \approx 40 - 60 days$ ). Displays low proarrhythmic Torsades de Pointes risk compared to other Class III agents, but carries multisystem toxicities:
- Pulmonary Toxicity: Chronic interstitial pneumonitis/fibrosis (requires baseline chest X-ray and pulmonary function tests).
- Thyroid Dysfunction: Amiodarone-Induced Hypothyroidism (AIH) or Amiodarone-Induced Thyrotoxicosis (AIT Type 1 vs Type 2; requires baseline and periodic TSH).
- Hepatic & Ocular: Elevated AST/ALT, corneal microdeposits (vortex keratopathy), optic neuropathy.
- Dermatologic: Photosensitivity and slate blue-gray skin discoloration.
- Drug Interactions: Potent inhibitor of CYP3A4, CYP2C9, and P-gp; doubles plasma concentrations of digoxin and warfarin (empirically reduce doses by $50\%$ ).

4. Endocrine Pharmacology: Diabetes Mellitus (Diabetes Canada Guidelines)

+--------------------------------------------------------------------------------------+
|                DIABETES CANADA TYPE 2 PHARMACOTHERAPY ALGORITHM                      |
+--------------------------------------------------------------------------------------+
|  FIRST-LINE: Healthy Behavior Interventions + Metformin (unless contraindicated)     |
|                                                                                      |
|  IF CLINICAL ASCVD, HEART FAILURE, OR CKD PRESENT (Independent of Baseline A1C):     |
|  +---> Clinical ASCVD  : SGLT2i (Empagliflozin) or GLP-1 RA (Liraglutide, Semaglutide)|
|  +---> Heart Failure   : SGLT2i (Dapagliflozin, Empagliflozin with proven HF benefit)|
|  +---> CKD (eGFR/ACR)  : SGLT2i (Canagliflozin, Dapagliflozin, Empagliflozin)        |
|                                                                                      |
|  OTHER SECOND-LINE (Glycemic Control Focus):                                         |
|  - DPP-4i (Sitagliptin, Linagliptin) | - GLP-1 RA | - SGLT2i                         |
|  - Gliclazide (Sulfonylurea)        | - Basal Insulin | - Pioglitazone (TZD)         |
+--------------------------------------------------------------------------------------+

Non-Insulin Antihyperglycemic Agents Matrix

Drug Class	Mechanism of Action	HbA1c Reduction	Weight Effect	Hypoglycemia Risk	Key Clinical Pearls & Safety Warnings
Biguanides (Metformin)	Activates AMPK $\to \downarrow$ hepatic gluconeogenesis, $\uparrow$ peripheral glucose uptake	$1.0-1.5\%$	Neutral / Mild loss	Negligible	First-line agent. Contraindicated if $\text{eGFR} < 30\text{ mL/min/1.73 m}^2$ due to lactic acidosis risk; reduce dose if $\text{eGFR} < 45$ . Hold prior to iodinated contrast. Causes vitamin B12 deficiency.
SGLT2 Inhibitors (Empagliflozin, Dapagliflozin, Canagliflozin)	Blocks SGLT2 in renal proximal tubule $\to$ blocks $90\%$ glucose reabsorption $\to$ glucosuria	$0.5-0.8\%$	Loss ( $2-3\text{ kg}$ )	Negligible	Proven reduction in MACE, CV death, HF hospitalization, and CKD progression. Adverse effects: Mycotic genital infections, volume depletion/orthostasis, euglycemic DKA (euDKA) (hold $3\text{ days}$ prior to elective surgery/acute illness).
GLP-1 Receptor Agonists (Semaglutide, Liraglutide, Dulaglutide)	Incretin mimetic: glucose-dependent insulin secretion, $\downarrow$ glucagon, delays gastric emptying	$1.0-1.8\%$	Significant loss ( $4-10+\text{ kg}$ )	Negligible	Proven ASCVD benefit. Contraindications: Personal/family history of Medullary Thyroid Carcinoma (MTC) or MEN-2; history of pancreatitis. Delays oral drug absorption.
DPP-4 Inhibitors (Sitagliptin, Linagliptin, Saxagliptin)	Inhibits DPP-4 enzyme, prolonging endogenous active GLP-1 and GIP incretin hormones	$0.5-0.7\%$	Neutral	Negligible	Well tolerated. Linagliptin requires no renal dose adjustment. Saxagliptin carries an increased risk of heart failure hospitalizations. Rare acute pancreatitis.
Sulfonylureas (Gliclazide, Glimepiride, Glyburide)	Binds SUR1 on pancreatic $\beta$ -cell $K_{\text{ATP}}$ channels $\to$ channel closure $\to$ depolarization $\to \uparrow$ insulin exocytosis	$0.8-1.2\%$	Gain	High	Gliclazide preferred over glyburide. Glyburide has active metabolites that accumulate in renal impairment, causing severe prolonged hypoglycemia.
Thiazolidinediones (Pioglitazone, Rosiglitazone)	PPAR- $\gamma$ nuclear receptor agonist $\to \uparrow$ insulin sensitivity in muscle/adipose	$0.8-1.2\%$	Gain	Negligible	Fluid retention and peripheral edema; contraindicated in NYHA Class III/IV Heart Failure. Increased fracture risk in females; bladder cancer warning (pioglitazone).

Insulin Formulations and Pharmacokinetics

\begin{aligned} \textbf{Ultra-Rapid / Rapid (Aspart, Lispro, Glulisine)} &: \text{Onset } 10-15\text{ min}, \text{Peak } 1-2\text{ h}, \text{Duration } 3-5\text{ h (Bolus / Prandial)} \\ \textbf{Short-Acting Regular (Humulin R, Novolin Toronto)} &: \text{Onset } 30-60\text{ min}, \text{Peak } 2-4\text{ h}, \text{Duration } 6-8\text{ h (IV Infusions in DKA)} \\ \textbf{Intermediate (NPH)} &: \text{Onset } 1-3\text{ h}, \text{Peak } 4-8\text{ h}, \text{Duration } 12-18\text{ h (Turbid suspension)} \\ \textbf{Long-Acting Basal (Glargine U100/U300, Detemir, Degludec)} &: \text{Onset } 1-2\text{ h}, \text{Peakless}, \text{Duration } 24-42+\text{ h (Degludec } t_{1/2} \approx 25\text{ h)} \end{aligned}

5. Thyroid and Adrenal Pharmacotherapy

Thyroid Pharmacotherapy: Hypothyroidism and Thyrotoxicosis

Levothyroxine ( $T_4$ ): Synthetic thyroxine, converted peripherally to active triiodothyronine ( $T_3$ ) by $5'$ -deiodinase. Half-life is $7\text{ days}$ ; steady-state requires $6-8\text{ weeks}$ . Narrow therapeutic index drug. Take once daily in the morning on an empty stomach with a full glass of water, $\ge 30-60\text{ minutes}$ before breakfast. Avoid co-administration within $4\text{ hours}$ of calcium, iron, magnesium, or bile acid sequestrants.
Thionamides (Methimazole vs. Propylthiouracil [PTU]):
- Inhibit thyroid peroxidase (TPO), blocking iodine organification and iodotyrosine coupling.
- Propylthiouracil (PTU) also inhibits peripheral $5'$ -deiodinase conversion of $T_4 \to T_3$ .
- Methimazole is first-line due to once-daily dosing and lower hepatotoxicity.
- PTU Indications: Preferred during the first trimester of pregnancy (methimazole causes embryopathy: aplasia cutis, choanal atresia) and in thyroid storm (due to peripheral $T_4 \to T_3$ inhibition). PTU carries a black-box warning for fulminant hepatic failure.
- Agranulocytosis: Rare ( $0.2-0.5\%$ ) life-threatening complication of both thionamides. Patients presenting with fever, chills, or sore throat must stop the drug immediately and obtain an urgent CBC with differential.

Test Your Knowledge

A 62-year-old patient with Heart Failure with Reduced Ejection Fraction (HFrEF, LVEF 28%) is being optimized on guideline-directed medical therapy. The cardiologist prescribes sacubitril/valsartan to replace ramipril 10 mg daily. Which instruction regarding the transition is critical to prevent a life-threatening adverse reaction?

A mandatory 36-hour washout period must elapse between the last dose of ramipril and the first dose of sacubitril/valsartan.

Sacubitril/valsartan should be initiated immediately at the next scheduled dosing interval without any washout period.

A 7-day loading phase of dual therapy with both ramipril and sacubitril/valsartan must be completed to ensure hemodynamic stability.

Sacubitril can be initiated as monotherapy while ramipril is gradually tapered over two weeks.

Test Your Knowledge

A 54-year-old patient with type 2 diabetes managed on metformin and empagliflozin presents to the emergency department with nausea, vomiting, tachypnea, and severe fatigue 48 hours following elective laparoscopic cholecystectomy. Laboratory analysis demonstrates an arterial pH of 7.22, serum bicarbonate of 11 mmol/L, serum beta-hydroxybutyrate of 4.8 mmol/L, and a blood glucose of 8.2 mmol/L. What physiological mechanism explains this patient's clinical state?

SGLT2 inhibitors directly stimulate pancreatic alpha-cell insulin secretion, resulting in paradoxical hyperinsulinemic ketoacidosis.

SGLT2 inhibitors induce glucosuria and decrease circulating insulin while increasing glucagon, promoting hepatic ketogenesis even with near-normal blood glucose levels.

SGLT2 inhibitors competitively inhibit hepatic mitochondrial beta-oxidation, leading to secondary accumulation of dicarboxylic ketoacids.

SGLT2 inhibitors block renal tubular excretion of acetoacetate and beta-hydroxybutyrate, causing accumulation of filtered organic anions.

Test Your Knowledge

A 68-year-old patient with hypertension is prescribed chlorthalidone 25 mg daily. Compared to loop diuretics such as furosemide, which metabolic and electrolyte pattern is uniquely characteristic of thiazide and thiazide-like diuretics?

Hyperkalemia and marked hypocalcemia due to proximal tubular calcium wasting

Hyperkalemic metabolic acidosis combined with severe hypermagnesemia

Hypokalemic metabolic alkalosis combined with hypercalcemia and hyponatremia

Severe hypernatremia and hypophosphatemia due to cortical collecting duct water loss

Test Your Knowledge

A 28-year-old woman in her sixth week of pregnancy is diagnosed with severe Graves' disease thyrotoxicosis. Which statement accurately reflects Canadian clinical guidelines regarding thionamide antithyroid drug selection and safety monitoring?

Methimazole is preferred throughout all trimesters of pregnancy due to zero risk of teratogenic congenital malformations.

Propylthiouracil is preferred for lifelong maintenance therapy in all adult patients due to a lower incidence of agranulocytosis compared to methimazole.

Methimazole is the thionamide of choice during acute thyroid storm because it uniquely blocks peripheral conversion of thyroxine to triiodothyronine.

Propylthiouracil is preferred during the first trimester of pregnancy and in thyroid storm, but carries a higher risk of fulminant hepatotoxicity compared to methimazole.

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4.3 Clinical Toxicology, Overdose Management, and Antidotes

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