Which of the following muscular relaxants causes hypotension and bronchospasm?

Correct Answer: C

Rationale: The correct answer is C: Tubocurarine. Tubocurarine is a non-depolarizing neuromuscular blocker that can cause hypotension and bronchospasm as side effects due to its mechanism of action on nicotinic receptors. A: Vecuronium is a non-depolarizing neuromuscular blocker but is less likely to cause hypotension and bronchospasm. B: Succinylcholine is a depolarizing neuromuscular blocker and does not typically cause hypotension and bronchospasm. D: Rapacuronium is a neuromuscular blocker that was withdrawn from the market due to the risk of severe bronchospasm.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. Metoprolol and atenolol are both selective beta1-adrenergic receptor antagonists. 2. Being beta1-selective means they primarily target beta1 receptors in the heart. 3. This results in decreased heart rate and reduced blood pressure. 4. Choice A is correct as it accurately describes the pharmacological action of metoprolol and atenolol. Summary of why other choices are incorrect: - Choice B (nonselective beta antagonists) is incorrect as metoprolol and atenolol are selective for beta1 receptors. - Choice C (intrinsic sympathomimetic activity) is incorrect as metoprolol and atenolol lack intrinsic sympathomimetic activity. - Choice D (anesthetic action) is incorrect as metoprolol and atenolol do not have anesthetic properties.

Correct Answer: A

Rationale: The correct answer is A: Triazolam. Triazolam has a short half-life, leading to quicker elimination from the body, which can cause a more pronounced "rebound" effect after discontinuation, resulting in rebound insomnia. Flurazepam and Temazepam have longer half-lives, so they are less likely to cause rebound insomnia. Choice D is incorrect as not all benzodiazepines cause rebound insomnia equally.

Correct Answer: B

Rationale: The correct answer is B: Carbamazepine. Carbamazepine is most commonly associated with the development of Steven-Johnson syndrome due to its high risk of causing severe hypersensitivity reactions. This drug has been widely reported to be a major cause of Steven-Johnson syndrome compared to the other options. Phenytoin (choice A) is known for causing different types of skin reactions but is less commonly linked to Steven-Johnson syndrome. Valproate (choice C) and Lamotrigine (choice D) have also been associated with skin reactions, but the incidence of Steven-Johnson syndrome with these drugs is lower compared to Carbamazepine.

Correct Answer: B

Rationale: The correct answer is B: Morphine. Morphine is a phenanthrene derivative as it belongs to the opioid class of analgesics derived from the phenanthrene nucleus. Fentanyl (A) is a synthetic opioid, not derived from phenanthrene. Methadone (C) is a synthetic opioid unrelated to phenanthrene. Pentazocine (D) is a mixed opioid agonist-antagonist, not a phenanthrene derivative. Therefore, based on the chemical structure and classification, morphine is the only phenanthrene derivative among the options.