Hormone analogues are:

Correct Answer: D

Rationale: The correct answer is D because hormone analogues are synthetic compounds that mimic the structure and function of naturally occurring hormones. This is important for therapeutic purposes as they can be used to replace or mimic the actions of hormones in the body. A is incorrect because hormone analogues are not naturally occurring substances but rather synthetic compounds. B is incorrect as hormone analogues can be equally or even more efficacious than naturally occurring hormones. C is incorrect because although hormone analogues may have similar structures to hormones, they do not necessarily have the same pharmacological properties.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Selective COX-2 inhibitors are safer than nonselective COX-1 inhibitors due to reduced risk of gastrointestinal side effects while maintaining efficacy. This is because COX-2 inhibitors target inflammation specifically, sparing COX-1 which is important for gastric mucosal protection. Nonselective COX-1 inhibitors can lead to gastric ulcers and bleeding. The other choices are incorrect: B: FALSE - selective COX-2 inhibitors are indeed safer than nonselective COX-1 inhibitors; C: None - this choice does not provide any information; D: All of the above - this choice is incorrect as only option A is true.

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: Rationale: 1. Vitamin C is known for its antioxidant properties, which help in neutralizing free radicals and protecting cells from damage. 2. It is required for hydroxylation reactions, such as converting proline to hydroxyproline for collagen synthesis, essential for maintaining connective tissues. 3. Vitamin C does not function as pyridoxal phosphate (choice A) or a constituent of coenzyme A (choice B). 4. While vitamin C is involved in one-carbon metabolism, it does not directly act as a carrier of one-carbon groups as described in choice C. Summary: The correct answer (D) highlights the antioxidant properties and the role of vitamin C in hydroxylation reactions for collagen synthesis. Choices A, B, and C are incorrect as they misrepresent the functions of vitamin C.

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.