Correct statements concerning lidocaine include all of the following EXCEPT:

Correct Answer: B

Rationale: The correct answer is B: It has esteratic linkage. Lidocaine is an amide-type local anesthetic, not an ester. It is not a universal anesthetic (A), as it is mainly used for local anesthesia. It is widely used as an antiarrhythmic agent (C) due to its ability to stabilize cell membranes in the heart. Lidocaine is metabolized in the liver (D) by the cytochrome P450 enzyme system. Therefore, B is incorrect because lidocaine does not have an esteratic linkage.

Correct Answer: C

Rationale: Rationale: 1. Ephedrine acts indirectly by stimulating release of norepinephrine from nerve terminals. 2. Epinephrine (A) and norepinephrine (B) act directly on adrenergic receptors. 3. Methoxamine (D) is a direct acting alpha-1 agonist. Summary: A, B, and D directly stimulate adrejsonceptors, while only C acts indirectly by promoting norepinephrine release.

Correct Answer: C

Rationale: The correct answer is C: Epinephrine. Epinephrine is a sympathomimetic agent that acts on both alpha and beta adrenergic receptors, increasing heart rate, contractility, and vasoconstriction. In cardiac arrest, epinephrine is crucial for improving coronary and cerebral perfusion, leading to increased chances of successful resuscitation. Methoxamine (A) and Phenylephrine (B) are pure alpha-adrenergic agonists with minimal cardiac effects, not ideal for cardiac arrest. Xylometazoline (D) is a nasal decongestant and has no role in cardiac arrest management.

Correct Answer: D

Rationale: The correct answer is D: Propranolol. Propranolol is the preferred beta-blocker for thyroid storm due to its non-selective beta-adrenergic blockade, which helps control symptoms such as tachycardia and hypertension. It also inhibits the peripheral conversion of T4 to T3. Pindolol (A) is a partial beta-blocker with intrinsic sympathomimetic activity, not ideal for thyroid storm. Sotalol (B) is a non-selective beta-blocker with class III antiarrhythmic properties, not typically used in thyroid storm. Phentolamine (C) is an alpha-blocker, not a beta-blocker, and not indicated for thyroid storm.

Correct Answer: C

Rationale: Certainly! Ethosuximide is the correct answer because it specifically targets T-type calcium channels in thalamic neurons, effectively controlling absence seizures. Carbamazepine, Lamotrigine, and Phenytoin primarily act on sodium channels, making them ineffective in treating absence seizures. Ethosuximide's mechanism of action makes it the ideal choice for this specific type of seizure.