Which of the following vitamins improves megaloblast anemia but does not protect the neurological manifestations of pernicious anemia?

Correct Answer: B

Rationale: The correct answer is B: Vitamin BC, also known as folic acid. Folic acid improves megaloblastic anemia by aiding in DNA synthesis. It does not protect against neurological manifestations of pernicious anemia because those are primarily caused by Vitamin B12 deficiency. Vitamin B12 is needed for nerve function and myelin synthesis. Vitamin PP refers to niacin, which is not directly related to these types of anemia. Vitamin D is important for bone health but is not directly involved in the treatment of megaloblastic anemia or pernicious anemia.

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.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Isoniazid is a first-line drug specifically used to treat mycobacterial infections like tuberculosis. 2. It works by inhibiting cell wall synthesis of mycobacteria. 3. Streptomycin, Rifampin, and Kanamycin are also used for mycobacterial infections, but they are effective against a broader range of bacteria. 4. Streptomycin targets protein synthesis, Rifampin inhibits RNA synthesis, and Kanamycin disrupts protein synthesis. 5. Therefore, choice A, Isoniazid, is the correct answer as it targets mycobacteria specifically.