Class of sirolimus (rapamycin) is:

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.

Correct Answer: B

Rationale: The correct answer is B: FALSE. Bile acid-binding resins work by binding bile acids in the intestine, not cholesterol directly. This binding leads to increased excretion of bile acids in feces and stimulates the liver to use more cholesterol to produce new bile acids, thus lowering blood cholesterol levels. Choice A is incorrect because bile acid-binding resins do not directly bind cholesterol. Choices C and D are incorrect as they do not accurately reflect the mechanism of action of bile acid-binding resins.

Correct Answer: D

Rationale: The correct answer is D. A: 1,25-dihydroxyvitamin D3 (calcitriol) is the active form of vitamin D and is the metabolite of choice for rapid action in raising serum calcium levels. B: Calcitriol does raise serum phosphate levels, but this effect may not be immediately observed. C: Calcitriol undergoes enterohepatic circulation, which means it is reabsorbed in the intestines and recycled through the liver. Therefore, all statements A, B, and C are true about 1,25-dihydroxyvitamin D3 (calcitriol), making option D the correct choice.

Correct Answer: A

Rationale: The correct answer is A: Acetazolamide (Diamox). Acetazolamide is a carbonic anhydrase inhibitor, primarily used to treat glaucoma and altitude sickness. Carbonic anhydrase is an enzyme that catalyzes the reversible hydration of carbon dioxide to bicarbonate and protons. By inhibiting this enzyme, acetazolamide reduces the production of aqueous humor in the eye and increases urinary bicarbonate excretion. Furosemide (B), Hydrochlorothiazide (C), and Spironolactone (D) are not carbonic anhydrase inhibitors and work through different mechanisms to treat conditions like hypertension and edema.

Correct Answer: C

Rationale: The correct answer is C: Erythromycin. Erythromycin is a macrolide antibiotic due to its macrocyclic lactone ring structure. Macrolides inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit. Neomycin (A) is an aminoglycoside, Doxycycline (B) is a tetracycline, and Cefotaxime (D) is a cephalosporin, none of which are macrolides. Thus, Erythromycin is the only drug among the options that belongs to the antibiotics-macrolides category.