This drug acts by inhibiting slow calcium channels in the SA and AV nodes:

Correct Answer: D

Rationale: Diltiazem is a calcium channel blocker that acts by inhibiting slow calcium channels in the SA and AV nodes, leading to decreased conduction velocity and reduced contractility of the heart muscle. This results in slowing of the heart rate and can be used to treat conditions such as supraventricular tachycardia. A: Quinidine is a Class I antiarrhythmic drug that works by blocking sodium channels. B: Adenosine acts on adenosine receptors and is used for the termination of supraventricular tachycardia. C: Flecainide is a Class Ic antiarrhythmic drug that blocks sodium channels. Therefore, the correct answer is Diltiazem (D) as it specifically targets calcium channels in the SA and AV nodes, distinguishing it from the other choices.

Correct Answer: D

Rationale: The correct answer is D. The oral route is not the preferred method of administering ACTH because it has poor oral bioavailability. ACTH is typically administered parenterally. A: True, endogenous ACTH is also known as corticotropin. B: Correct, ACTH stimulates corticosteroid synthesis. C: True, ACTH is clinically useful in diagnosing adrenal insufficiency. Therefore, choice D is incorrect due to poor oral bioavailability compared to parenteral routes.

Correct Answer: B

Rationale: Certainly! Glucagon can be used in severe hyperglycemia because it stimulates the liver to release glucose into the bloodstream, helping to lower blood sugar levels. In contrast, using glucagon for severe hypoglycemia can worsen the condition by further decreasing blood sugar levels. It is not typically used for endocrine diagnosis or beta-blocker poisoning as there are more effective treatments available for these situations.

Correct Answer: A

Rationale: The correct answer is A: Piroxicam. Piroxicam is a nonselective COX inhibitor because it inhibits both COX-1 and COX-2 enzymes. This makes it effective for reducing inflammation by blocking prostaglandin synthesis. Rofecoxib (B) is a selective COX-2 inhibitor, while Celecoxib (C) is also a selective COX-2 inhibitor. Therefore, choices B and C are incorrect. Choice D is incorrect as well because not all listed NSAIDs are nonselective COX inhibitors.

Correct Answer: C

Rationale: The correct answer is C: Immunosuppressive agents. Sirolimus belongs to the class of immunosuppressive agents because it inhibits the activity of T-lymphocytes and prevents rejection of transplanted organs. It does not belong to the classes of A: Immunoglobulins, B: Interferons, or D: Monoclonal antibodies, as these are not mechanisms of action associated with sirolimus. Immunoglobulins are antibodies, interferons are signaling proteins, and monoclonal antibodies are targeted therapies. Therefore, the most appropriate classification for sirolimus is as an immunosuppressive agent.