Which of the following drugs is a thromboxane A2 receptor (TXA2) antagonist?

Correct Answer: A

Rationale: Step 1: Thromboxane A2 (TXA2) is a potent vasoconstrictor and platelet aggregator. Step 2: Sulotroban is a specific TXA2 receptor antagonist, blocking its effects. Step 3: Zileuton inhibits 5-lipoxygenase, not directly related to TXA2 receptors. Step 4: Zafirleukast is a leukotriene receptor antagonist, not targeting TXA2 receptors. Step 5: Diclofenac is a non-selective NSAID, not a TXA2 receptor antagonist. Summary: Sulotroban is the correct choice as it directly blocks TXA2 receptors, while the other options target different pathways.

Correct Answer: B

Rationale: Step 1: Taurine is a vitamin-like compound as it is an amino acid that has functions similar to vitamins in the body. Step 2: Ascorbic acid (Vitamin C) is a vitamin, not a vitamin-like compound. Step 3: Thiamine (Vitamin B1) and Riboflavin (Vitamin B2) are both vitamins, not vitamin-like compounds. Summary: Taurine is the correct answer as it is an amino acid with functions similar to vitamins, while the other choices are known vitamins.

Correct Answer: A

Rationale: Step-by-step rationale: 1. HMG-CoA reductase inhibitors like statins can cause muscle breakdown. 2. Cyclosporine is known to increase the risk of muscle breakdown when used with statins. 3. Thus, the statement that HMG-CoA reductase inhibiting drugs can cause muscle breakdown, especially when used with cyclosporine, is TRUE. Summary: Choice A is correct because it aligns with the known pharmacological interactions between HMG-CoA reductase inhibitors and cyclosporine. Choices B, C, and D are incorrect as they do not accurately reflect the specific relationship between these drugs and muscle breakdown.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Dihydrotachysterol is a form of vitamin D used to treat hypoparathyroidism. 2. Anorexia is a common unwanted effect due to increased calcium absorption causing decreased appetite. 3. Tetany is incorrect as vitamin D helps maintain calcium levels to prevent tetany. 4. CNS toxicity is incorrect as dihydrotachysterol does not typically affect the central nervous system. 5. Lymphocytopenia is incorrect as it is not a known side effect of dihydrotachysterol. Summary: The correct answer is B because anorexia is a common unwanted effect of dihydrotachysterol due to increased calcium absorption, while the other choices are incorrect as they do not align with the mechanism of action or known side effects of this medication.

Correct Answer: D

Rationale: Rationale for Correct Answer D: Aldosterone is a hormone that regulates salt and water balance by affecting sodium and potassium levels. Hydrochlorothiazide inhibits sodium reabsorption, while amiloride blocks potassium excretion. Since aldosterone promotes sodium reabsorption and potassium excretion, the presence of aldosterone would counteract the effects of both drugs. Therefore, the correct answer is D, as neither drug requires aldosterone for effectiveness. Choice A (Hydrochlorothiazide) is incorrect because it works independently of aldosterone by inhibiting sodium reabsorption in the kidneys. Choice B (Amiloride) is also incorrect as it directly blocks sodium channels in the kidneys, regardless of aldosterone levels. Choice C is incorrect because both drugs are effective regardless of aldosterone presence.