Which of the following statements is not correct for local anesthetics?

Correct Answer: B

Rationale: The correct answer is B. Charged cationic forms of local anesthetics do not penetrate biological membranes more readily than uncharged forms. This is because charged molecules have difficulty crossing cell membranes due to their polarity. In contrast, uncharged forms easily pass through lipid membranes. Therefore, statement B is incorrect. Statements A, C, and D are correct. A is true because local anesthetics can exist in both uncharged and cationic forms in tissues. C is true because local anesthetics are less effective in inflamed tissues due to increased acidity and altered tissue permeability. D is true because low pH in inflamed tissues inhibits the dissociation of nonionized molecules, reducing the effectiveness of local anesthetics.

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.

Correct Answer: A

Rationale: The correct answer is A: Zolpidem. Zolpidem is preferred in patients with limited hepatic function because it undergoes minimal hepatic metabolism, making it less dependent on liver function for elimination. This reduces the risk of drug accumulation and potential toxicity in patients with hepatic impairment. Amobarbital (B), Flurazepam (C), and Pentobarbital (D) are all barbiturates that are extensively metabolized in the liver. Therefore, they are not preferred in patients with limited hepatic function as their metabolism can be impaired, leading to increased drug levels and potential toxicity.