What does “affinity” mean?

Correct Answer: B

Rationale: The correct answer is B because "affinity" refers to how tightly a drug binds to a receptor. This is crucial for the drug to exert its pharmacological effect. A: Plasma protein binding is not specifically related to affinity but affects drug distribution. C: Inhibiting potency is different from affinity, which is about binding strength. D: Bioavailability is about drug absorption, not binding to receptors. Thus, B is the most appropriate choice.

Correct Answer: D

Rationale: In pharmacology, cholinesterase inhibitors are classified as reversible or irreversible based on their mechanism of action. In this case, the correct answer is D) Isoflurophate because it is an irreversible cholinesterase inhibitor. Irreversible cholinesterase inhibitors form a strong covalent bond with the enzyme acetylcholinesterase, leading to a long-lasting inhibition of the enzyme's activity. This results in an accumulation of acetylcholine at cholinergic synapses, prolonging its action. Physostigmine (A), Edrophonium (B), and Neostigmine (C) are all reversible cholinesterase inhibitors. They form weaker, reversible bonds with acetylcholinesterase, allowing the enzyme to recover its activity over time. Understanding the distinction between reversible and irreversible cholinesterase inhibitors is crucial in pharmacology, especially in the context of treating conditions like myasthenia gravis or reversing neuromuscular blockade. Practitioners must be aware of the differences in potency, duration of action, and potential side effects associated with each type of inhibitor to make informed clinical decisions.

Correct Answer: A

Rationale: The correct answer is A: Mecamylamine. Mecamylamine is a ganglion-blocking drug that can be taken orally for hypertension. It blocks nicotinic acetylcholine receptors in autonomic ganglia, leading to decreased sympathetic tone and vasodilation, which helps reduce blood pressure. Scopolamine (B) is an anticholinergic drug used for motion sickness, trimethaphane (C) is a ganglion-blocking drug but not suitable for oral administration, and vecuronium (D) is a neuromuscular blocking agent used during surgery.

Correct Answer: C

Rationale: The correct answer is C: Epinephrine. Epinephrine is an alpha1, alpha2, beta1, and beta2 receptor agonist. It acts on all four types of adrenergic receptors, making it unique among the choices. Methoxamine is a selective alpha1 agonist (A). Albuterol is a beta2 agonist (B). Norepinephrine is an alpha1, alpha2, and beta1 agonist, but not a beta2 agonist (D). Therefore, only epinephrine fits the criteria of being an alpha1, alpha2, beta1, and beta2 receptor agonist.

Correct Answer: C

Rationale: The correct answer is C: Phentolamine. Phentolamine is an alpha-adrenergic antagonist that helps block the effects of excess catecholamines released by pheochromocytoma. It helps to control hypertension and other symptoms associated with pheochromocytoma. A: Phenylephrine is an alpha-1 adrenergic agonist, which would worsen hypertension in pheochromocytoma. B: Propranolol is a beta-blocker, which can lead to unopposed alpha-adrenergic effects and exacerbate hypertension in pheochromocytoma. D: Epinephrine is a catecholamine that would exacerbate symptoms in pheochromocytoma due to its stimulatory effects on alpha and beta adrenergic receptors.