Patients complain of dry or “sandy” eyes when receiving large doses of:

Correct Answer: A

Rationale: The correct answer is A: Atropine. Atropine is an anticholinergic medication that blocks the action of acetylcholine, leading to decreased tear production and dry eyes. This is why patients complain of dry or "sandy" eyes when receiving large doses of Atropine. Summary of other choices: B: Hexamethonium - This is a ganglionic blocking agent used in hypertension, not associated with dry eyes. C: Pilocarpine - This is a cholinergic agonist used to treat glaucoma by increasing tear production, opposite effect of dry eyes. D: Carbachol - This is a cholinergic agonist used in glaucoma, not associated with dry eyes.

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.

Correct Answer: B

Rationale: The correct answer is B because the principal aim for treating Parkinsonian disorders is to restore dopaminergic activity with levodopa and dopamine agonists. This is because Parkinson's disease is primarily caused by a deficit of dopamine in the brain. Levodopa is converted to dopamine in the brain, helping to alleviate symptoms. Choice A is incorrect because antimuscarinic drugs target the cholinergic system, not the dopaminergic system, and are not the primary treatment for Parkinson's disease. Choice C is incorrect because glutamate antagonists target a different neurotransmitter system and are not the mainstay of treatment for Parkinson's disease. Choice D is incorrect because while restoring balance between cholinergic and dopaminergic influences may be important, the primary aim is to address the dopaminergic deficit.