Which of the following medications does the nurse identify as a calcium channel blocker used to treat tachycardia and manage heart rate?
Digoxin
Diltiazem (Cardizem)
Nitroglycerin
Nitroprusside (Nipride)
The Correct Answer is B
Choice A rationale:
Digoxin is a cardiac glycoside, not a calcium channel blocker. It works by increasing the force of contraction of the heart muscle and slowing the heart rate. However, it is not typically used as a first-line treatment for tachycardia. It's more commonly used to treat heart failure and atrial fibrillation.
Mechanism of action: Digoxin inhibits the sodium-potassium ATPase pump in cardiac cells, leading to an increase in intracellular calcium. This increased calcium availability enhances myocardial contractility. Digoxin also indirectly affects the autonomic nervous system, leading to a decrease in heart rate.
Key points:
Digoxin is not a calcium channel blocker.
It's used primarily for heart failure and atrial fibrillation.
Its mechanism of action involves increasing intracellular calcium and decreasing heart rate.
Choice B rationale:
Diltiazem (Cardizem) is a calcium channel blocker that is commonly used to treat tachycardia and manage heart rate. It works by blocking the movement of calcium into cardiac cells, which slows down the electrical conduction system of the heart and leads to a decrease in heart rate.
Mechanism of action: Diltiazem blocks L-type calcium channels in cardiac and vascular smooth muscle cells. This reduces calcium influx, leading to:
Decreased myocardial contractility Vasodilation (relaxation of blood vessels)
Negative chronotropic effect (decreased heart rate)
Negative dromotropic effect (slowed conduction through the AV node) Key points:
Diltiazem is a calcium channel blocker.
It's effective in treating tachycardia and managing heart rate.
Its mechanism of action involves blocking calcium channels, leading to various cardiovascular effects.
Choice C rationale:
Nitroglycerin is a vasodilator, not a calcium channel blocker. It works by relaxing the smooth muscle in blood vessels, which widens the vessels and allows more blood to flow through them. This can help to relieve chest pain (angina) and lower blood pressure, but it does not directly affect heart rate.
Mechanism of action: Nitroglycerin is metabolized to nitric oxide, which activates guanylate cyclase, leading to increased production of cyclic guanosine monophosphate (cGMP). cGMP causes smooth muscle relaxation, resulting in vasodilation.
Key points:
Nitroglycerin is a vasodilator, not a calcium channel blocker. It's primarily used for angina and hypertension.
Its mechanism of action involves nitric oxide-mediated vasodilation.
Choice D rationale:
Nitroprusside (Nipride) is a potent vasodilator, not a calcium channel blocker. It is typically used in critical care settings to manage severe hypertension or heart failure. It works by relaxing the smooth muscle in blood vessels, which widens the vessels and allows more blood to flow through them. This can help to lower blood pressure, but it does not directly affect heart rate.
Mechanism of action: Nitroprusside directly releases nitric oxide, leading to vasodilation. Key points:
Nitroprusside is a potent vasodilator, not a calcium channel blocker.
It's used in critical care settings for severe hypertension or heart failure.
Its mechanism of action involves direct nitric oxide release and vasodilation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale:
Propylthiouracil (PTU) is a thionamide medication that inhibits the synthesis of thyroid hormones. It is the preferred drug for presurgical treatment of Graves' disease because it effectively lowers thyroid hormone levels and reduces the risk of thyroid storm, a life-threatening complication that can occur during or after surgery.
PTU acts by blocking the enzyme thyroid peroxidase, which is essential for the production of thyroid hormones. It also inhibits the conversion of thyroxine (T4) to triiodothyronine (T3), the more active form of thyroid hormone. This results in a decrease in circulating levels of both T4 and T3, leading to a reduction in the symptoms of hyperthyroidism.
PTU is typically started at a dose of 100-300 mg daily, divided into two or three doses. The dose is then adjusted based on the patient's response and thyroid hormone levels. The goal of treatment is to achieve a euthyroid state, which means that the thyroid hormone levels are within the normal range.
PTU is generally well-tolerated, but it can cause some side effects, including skin rash, itching, nausea, vomiting, abdominal pain, joint pain, and hair loss. In rare cases, it can also cause serious side effects, such as liver damage and agranulocytosis (a decrease in white blood cells).
Choice B rationale:
Liotrix (Thyrolar) is a combination of synthetic T4 and T3 hormones. It is not used for presurgical treatment of Graves' disease because it can worsen the symptoms of hyperthyroidism.
Choice C rationale:
Propranolol (Inderal) is a beta-blocker medication that can be used to control the symptoms of hyperthyroidism, such as tachycardia, tremor, and anxiety. However, it does not lower thyroid hormone levels and is not used for presurgical treatment of Graves' disease.
Choice D rationale:
Levothyroxine sodium (Synthroid) is a synthetic T4 hormone. It is used to treat hypothyroidism, but it is not used for presurgical treatment of Graves' disease.
Correct Answer is A
Explanation
Choice A rationale:
Sildenafil (Viagra) is a phosphodiesterase-5 (PDE-5) inhibitor that is primarily used to treat erectile dysfunction. However, it also has vasodilatory effects, meaning it widens blood vessels. This can lead to a significant drop in blood pressure, especially when combined with nitroglycerin, another potent vasodilator.
Nitroglycerin is commonly used to treat chest pain (angina) and heart failure. It works by relaxing the smooth muscles in blood vessels, which allows them to widen and increase blood flow to the heart. This can help to relieve chest pain and improve heart function.
When sildenafil and nitroglycerin are taken together, their combined vasodilatory effects can cause a severe drop in blood pressure, known as hypotension. This can lead to a number of serious complications, including: dizziness, lightheadedness, fainting, heart attack, stroke.
The risk of hypotension is particularly high in patients who are already taking other medications that can lower blood pressure, such as alpha-blockers or nitrates. It is also important to note that the effects of sildenafil can last for up to 24-48 hours, so it is important to avoid taking nitroglycerin within this timeframe.
Due to the significant risk of hypotension, it is generally recommended that sildenafil be avoided within 24-48 hours of nitroglycerin administration.
Rationales for other choices:
Choice B: Aspirin
Aspirin is an antiplatelet medication that is often used to prevent blood clots. It does not have significant vasodilatory effects and does not interact with nitroglycerin in a way that would contraindicate its use.
Choice C: Adenosine
Adenosine is a medication that is used to treat certain types of arrhythmias (irregular heartbeats). It can cause a brief drop in blood pressure, but this effect is usually mild and transient. Adenosine does not interact with nitroglycerin in a way that would contraindicate its use.
Choice D: Oxygen
Oxygen is a gas that is often used to treat patients with respiratory problems. It does not have any direct vasodilatory effects and does not interact with nitroglycerin.
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