Mechanism of action of cyclosporine A is:

Correct Answer: C

Rationale: The correct answer is C: Inhibits calcineurin. Cyclosporine A works by inhibiting calcineurin, a protein phosphatase that is crucial for the activation of T cells. By blocking calcineurin, cyclosporine A prevents the production of interleukin-2, a key cytokine involved in T cell activation and proliferation. This ultimately leads to suppression of the immune response. Choices A, B, and D are incorrect: A: Complement-mediated cytolysis of T lymphocytes is not the mechanism of action of cyclosporine A. B: ADCC towards T lymphocytes does not describe how cyclosporine A works. D: Competing for Fc receptors with autoantibodies is not related to the mechanism of action of cyclosporine A.

Correct Answer: D

Rationale: The correct answer is D. Drugs that inhibit cholesterol synthesis, such as statins, do not tend to lengthen the sleep cycle. Statins are not known to have a direct effect on sleep patterns. Choices A, B, and C are true statements regarding drugs inhibiting cholesterol synthesis. Choice A is correct as these drugs are contraindicated in pregnant women and children due to potential harm to fetal development. Choice B is correct as statins can cause myopathy, especially when used with cyclosporine. Choice C is correct as failure to discontinue the drug after myopathy has been detected can lead to acute renal failure.

Correct Answer: B

Rationale: The correct route of administration for vitamin D3 is oral (Choice B) because it is a fat-soluble vitamin that can be effectively absorbed through the digestive system. Subcutaneous (Choice A) and intravenous (Choice C) routes are not typically used for vitamin D3 as it can lead to potential risks and complications. Intranasal (Choice D) administration is not a common route for vitamin D3 absorption, as it may not provide adequate bioavailability compared to oral ingestion. Therefore, the oral route is the most appropriate and efficient method for administering vitamin D3.

Correct Answer: D

Rationale: The correct answer is D: Fractures. Plicamycin is not known to cause fractures. Thrombocytopenia, GI toxicity, and bleeding disorders are potential unwanted effects of plicamycin due to its impact on bone marrow and gastrointestinal tract. It is crucial to recognize that fractures are not a documented side effect of plicamycin, making option D the correct answer.

Correct Answer: D

Rationale: Rationale: 1. Choice A is correct because combining antimicrobial agents can enhance their effectiveness against resistant strains. 2. Choice B is correct because a combination can target a wider range of microorganisms. 3. Choice C is correct because using a combination can help reduce the chance of resistance developing. Summary: All of the above choices are correct because rational antimicrobial combinations provide synergism, broad coverage, and prevent resistance emergence.