Indicate a reversible cholinesterase inhibitor:

Correct Answer: C

Rationale: Physostigmine is the correct answer as it is a reversible cholinesterase inhibitor. This means it binds to the enzyme temporarily and can be easily displaced, allowing the enzyme to function normally after a while. Physostigmine is commonly used in the treatment of glaucoma and myasthenia gravis. A: Isoflurophate is an irreversible cholinesterase inhibitor, meaning it forms a permanent bond with the enzyme. B: Carbochol is a direct-acting cholinergic agonist, not a cholinesterase inhibitor. D: Parathion is an organophosphate insecticide that irreversibly inhibits cholinesterase enzymes.

Correct Answer: A

Rationale: The correct answer is A: Norepinephrine. Norepinephrine is a direct-acting alpha-1 and beta-1 receptor agonist. It stimulates both alpha and beta receptors directly, leading to vasoconstriction (via alpha-1) and increased heart rate and contractility (via beta-1). Methoxamine (B) is a selective alpha-1 agonist, Isoproterenol (C) is a non-selective beta agonist, and Ephedrine (D) is a mixed-acting sympathomimetic drug with indirect effects. Therefore, norepinephrine is the only choice that directly acts on both alpha and beta receptors.

Correct Answer: B

Rationale: The correct answer is B because alpha-receptor antagonists block alpha2 receptors on vascular smooth muscle, preventing vasoconstriction caused by epinephrine and reducing blood pressure in patients with pheochromocytoma. This helps manage symptoms of hypertension and tachycardia associated with excessive catecholamine release. Incorrect choices: A: Alpha-receptor antagonists do not inhibit the release of epinephrine from the adrenal medulla. C: Alpha-receptor antagonists do not interact with or inhibit beta2 adrenoreceptors. D: Alpha-receptor antagonists do not antagonize the release of renin.

Correct Answer: C

Rationale: The correct answer is C: Temazepam. Temazepam is preferred for elderly patients due to its shorter half-life, reduced risk of accumulation, and lower potential for drug interactions compared to other options. Phenobarbital (A) and Secobarbital (D) have long half-lives, leading to increased risk of side effects and drug interactions in the elderly. Flurazepam (B) has a long half-life and can cause residual sedation, increasing the risk of falls and cognitive impairment in the elderly.

Correct Answer: C

Rationale: The correct answer is C, Lamotrigine. Lamotrigine is a phenyltriazine derivative, making it the antiseizure drug in the list. This drug works by stabilizing neuronal membranes and inhibiting voltage-gated sodium channels. Phenobarbital (A) is a barbiturate, Clonazepam (B) is a benzodiazepine, and Carbamazepine (D) is an iminostilbene derivative, not a phenyltriazine derivative like Lamotrigine.