A patient with Graves’ disease exhibits symptoms of tachycardia, heat intolerance, and exophthalmos. Which drug is used to alter thyroid hormone levels prior to surgery?

Choice A rationale:

Insulin is a protein-based hormone that is sensitive to heat and light. Exposure to high temperatures or direct sunlight can cause insulin to break down and become less effective.

Refrigeration helps to maintain the stability and potency of insulin. It is generally recommended to store unopened insulin vials in the refrigerator at a temperature between 36°F and 46°F (2°C and 8°C).

This temperature range helps to slow down the degradation process and ensure that the insulin remains effective until its expiration date.

Choice B rationale:

Insulin should never be frozen. Freezing can cause the insulin to crystallize and become unusable. Once insulin has been frozen, it cannot be thawed and used again.

Choice C rationale:

Opened vials of insulin do not need to be discarded immediately. They can be stored in the refrigerator for up to 28 days, depending on the type of insulin.

However, it is important to note the date that the vial was opened and to discard it after the recommended storage period.

Choice D rationale:

Insulin pens should be stored according to the manufacturer’s instructions. Some insulin pens can be stored at room temperature for a certain period of time, while others must be refrigerated.

It is important to read the instructions that come with the insulin pen to ensure that it is stored properly.

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.