Metoprolol and atenolol:

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: 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.

Correct Answer: C

Rationale: The correct answer is C: Aspirin. Salicylic acid is the parent compound of aspirin. Aspirin is a salicylic acid derivative commonly used for its anti-inflammatory and analgesic properties. Phenylbutazone (A) is a pyrazolone derivative, Ketamine (B) is a dissociative anesthetic, and Tramadol (D) is a synthetic opioid. Aspirin's chemical structure contains the salicylic acid moiety, making it the only salicylic acid derivative among the options provided.

Correct Answer: B

Rationale: The correct answer is B: Decrease catecholamine-related activity. Lithium is known to decrease the activity of catecholamines, including norepinephrine and dopamine, by inhibiting their release and synthesis. This action helps in stabilizing mood and is why lithium is commonly used in the treatment of bipolar disorder. A: Stimulating dopamine and beta-adrenergic receptors is incorrect as lithium does not directly affect these receptors. C: Stimulating the development of dopamine receptor supersensitivity is incorrect as lithium does not enhance dopamine receptor sensitivity. D: Decreasing cholinergic activity is incorrect as lithium primarily affects catecholamines, not cholinergic neurotransmission.