The major causes of hypocalcemia in the adult are:

Correct Answer: D

Rationale: The correct answer is D, as hypocalcemia in adults can result from various causes. Hypoparathyroidism leads to decreased parathyroid hormone and calcium levels. Vitamin D deficiency impairs calcium absorption. Renal failure and malabsorption can disrupt calcium balance. Therefore, all options A, B, and C contribute to hypocalcemia in adults. Other choices are incorrect because they do not comprehensively cover the major causes of hypocalcemia in adults.

Correct Answer: B

Rationale: The correct answer is B: Pancytopenia. Chloramphenicol is known to cause bone marrow suppression, leading to a decrease in red blood cells, white blood cells, and platelets. This results in pancytopenia, which can manifest as anemia, increased risk of infections, and easy bruising or bleeding. Nephrotoxicity (A), hepatotoxicity (C), and ototoxicity (D) are not common side effects of chloramphenicol. Pancytopenia is a well-documented adverse effect of this antibiotic due to its impact on bone marrow function.

Correct Answer: B

Rationale: The correct answer is B: Headache, dizziness, insomnia. Fluoroquinolones are known to cause central nervous system side effects such as headache, dizziness, and insomnia. These unwanted effects are commonly reported with the use of fluoroquinolones. Hallucinations (choice A) are not typically associated with fluoroquinolones. Hypertension (choice C) is not a common side effect of fluoroquinolones. Immunetoxicity (choice D) is a general term and not a specific unwanted effect of fluoroquinolones. Therefore, choice B is the correct answer due to the known side effects of fluoroquinolones on the central nervous system.

Correct Answer: A

Rationale: Acyclovir is an antiviral drug used to treat herpes infections, not influenza. Amantadine and Rimantadine are anti-influenza agents that target the influenza A virus. Interferons are proteins that help the immune system fight viruses, including influenza. Therefore, the correct answer is A (Acyclovir) because it is not used specifically to treat influenza infections.

Correct Answer: C

Rationale: Rationale: 1. Digoxin inhibits Na+/K+ ATPase, leading to intracellular Na+ accumulation. 2. Increased intracellular Na+ reduces the activity of Na+/Ca2+ exchanger, causing Ca2+ to remain in the cell. 3. Elevated intracellular Ca2+ levels enhance cardiac contractility, resulting in positive inotropic effects. Summary: A: Closing of calcium channels would decrease Ca2+ influx, contrary to the inotropic effect. B: Increased release of Ca2+ from the sarcoplasmic reticulum is not the primary mechanism of digoxin's action. D: Activation of the Ca2+/Na+ exchanger would lead to Ca2+ extrusion, opposing the inotropic effect.