What term is used to describe a decrease in responsiveness to a drug which develops in a few minutes?

Correct Answer: D

Rationale: The correct answer is D: Tachyphylaxis. Tachyphylaxis refers to a rapid decrease in response to a drug that develops within minutes. This term specifically describes the phenomenon of developing a tolerance to a drug in a short period of time. Refractoriness (A) generally refers to a lack of response to a drug over time. Cumulative effect (B) is the gradual build-up of a drug's effects with repeated doses. Tolerance (C) is the gradual decrease in response to a drug over an extended period, not within minutes. Thus, the most appropriate term for a rapid decrease in responsiveness to a drug is tachyphylaxis.

Correct Answer: B

Rationale: Benztropine is the correct answer as it acts as both a muscarinic and nicotinic blocker. Benztropine primarily blocks muscarinic receptors, leading to decreased parasympathetic activity. It also has some nicotinic blocking effects, particularly at higher doses. Atropine (choice A) is a muscarinic antagonist only, while Hexamethonium (choice C) and Succinylcholine (choice D) are nicotinic antagonists only.

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 D: Rapacuronium is a neuromuscular blocker that was withdrawn from the market due to the risk of severe bronchospasm.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: C

Rationale: The correct answer is C because salmeterol does not stimulate heart rate, contractility, or cardiac output. Salmeterol is a long-acting beta2 agonist that primarily acts on the bronchial smooth muscles to provide bronchodilation in conditions like asthma and chronic obstructive pulmonary disease. Choice A is incorrect because salmeterol is indeed a potent selective beta2 agonist. Choice B is also incorrect as salmeterol does not cause uterine relaxation. Choice D is incorrect as salmeterol is commonly used in the therapy of asthma to provide long-term symptom control.

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.