Which of the following actions best explains the potassium-sparing effect of triamterene in the 66-year-old woman with systolic cardiac failure?

Correct Answer: B

Rationale: The correct answer is B: Blockade of Na+ channels in the collecting duct. Triamterene is a potassium-sparing diuretic that works by inhibiting the epithelial sodium channels (ENaC) in the collecting duct of the nephron. By blocking these channels, triamterene reduces sodium reabsorption, leading to decreased potassium excretion. This mechanism helps maintain potassium levels in the body, making it an effective treatment for conditions like systolic cardiac failure where potassium loss is a concern. Summary: A: Enhancement of K+ reabsorption in the proximal tubule - This is incorrect as triamterene does not act on the proximal tubule for potassium-sparing effects. C: Enhancement of K+ reabsorption in the loop of Henle - This is incorrect as triamterene does not primarily affect potassium reabsorption in the loop of Henle. D: Blockade of aldosterone receptors in the collecting duct - This is

Correct Answer: A

Rationale: In this question, the correct answer is A) Moxonidine. Moxonidine is a selective agonist of the imidazoline receptor, specifically the I1 subtype. This receptor is involved in the regulation of blood pressure and cardiovascular function. Moxonidine acts centrally to decrease sympathetic outflow, leading to vasodilation and reduced blood pressure. Option B) Dexmedetomidine is a selective agonist of the α2-adrenergic receptor and is commonly used as a sedative in intensive care settings. While it does have some effects on blood pressure regulation, it does not act on imidazoline receptors. Option C) Tizanidine is a centrally acting alpha-2 adrenergic agonist primarily used as a muscle relaxant. It does not target imidazoline receptors. Therefore, the correct answer is A) Moxonidine because it specifically targets the imidazoline receptor, while the other options act on different receptors with distinct physiological effects. Understanding the specific mechanisms of action of cardiovascular drugs is crucial for healthcare professionals to make informed decisions when managing patients with cardiovascular conditions.

Correct Answer: C

Rationale: Rationale: The correct answer is C) Cumulative poisoning. Digitalis, a medication derived from the foxglove plant, is commonly used to treat various heart conditions like heart failure and atrial fibrillation. Overuse of digitalis can lead to cumulative poisoning due to its narrow therapeutic index, meaning there is a fine line between a therapeutic dose and a toxic dose. Option A) Habituation refers to the body's decreased response to a drug over time, requiring higher doses to achieve the same effect. This is not the case with digitalis. Option B) Tolerance occurs when the body becomes accustomed to a drug's effects, also leading to the need for higher doses to achieve the same response. However, digitalis toxicity is more about the drug building up in the body to toxic levels rather than tolerance development. Option D) Physical dependence is a state where the body adapts to a drug and requires it to function normally. Digitalis toxicity is not primarily about physical dependence but rather the toxic effects of the drug accumulating in the body. Educational Context: It is crucial for healthcare professionals to understand the potential risks associated with medications like digitalis to prevent adverse effects such as cumulative poisoning. Monitoring patients closely, conducting regular drug level checks, and educating patients on signs of toxicity are essential in managing cardiovascular drug therapy effectively. Understanding the mechanisms of drug actions and potential side effects is vital for safe and effective patient care.

Correct Answer: D

Rationale: In the treatment of atrial fibrillation, digitalis is given before quinidine because digitalis increases A-V conduction and counteracts the 'vagolytic' effect of quinidine, preventing paradoxic tachycardia. This is the correct answer (Option D). Option A is incorrect because quinidine has a 'vagolytic' effect, not a 'vagotonic' effect. Option B is incorrect because quinidine does not have a 'vagolytic' effect that would cause paradoxic bradycardia. Option C is incorrect because quinidine does not have a 'vagotonic' effect that would lead to paradoxic bradycardia. In an educational context, understanding the pharmacological effects of digitalis and quinidine in the treatment of atrial fibrillation is crucial for healthcare professionals. Digitalis helps to improve A-V conduction, while quinidine has effects on vagal tone. Knowing the rationale behind the order of administration of these drugs can help in managing patients with atrial fibrillation effectively.

Correct Answer: C

Rationale: In the context of cardiovascular drugs, understanding the potential adverse effects of medications like dobutamine is crucial for safe and effective patient care. Correct Answer (C - Tachycardia): - Dobutamine is a beta-1 adrenergic agonist that primarily increases heart rate and contractility. Therefore, tachycardia is an expected adverse effect of this medication. Incorrect Answers: - A) Heart failure: Dobutamine is actually often used to treat acute heart failure due to its positive inotropic effects. - B) Bradycardia: Dobutamine typically increases heart rate, so bradycardia would be an unexpected adverse effect. - D) Respiratory distress: While some cardiovascular drugs can cause respiratory issues, this is not a common adverse effect of dobutamine. Educational Context: Understanding the mechanism of action of cardiovascular drugs like dobutamine is essential for predicting their potential side effects. By knowing that dobutamine increases heart rate and contractility, healthcare providers can anticipate and monitor for tachycardia as an adverse effect. This knowledge helps in providing safe and individualized care to patients receiving such medications.