Correct Answer: A

Rationale: Quinidine is classified as a class IA sodium channel blocker. Class IA antiarrhythmics, like quinidine, work by blocking sodium channels and delaying repolarization. Propafenone, mentioned in the original rationale, is actually a class IC antiarrhythmic agent, not a class IA sodium channel blocker.

Correct Answer: A

Rationale: Insomnia is a common symptom of levothyroxine overdose due to excessive stimulation of the central nervous system. Levothyroxine is a thyroid hormone replacement medication, and an overdose can lead to hyperthyroidism symptoms, including insomnia. Constipation and drowsiness are not typically associated with levothyroxine overdose. Hypoactive deep-tendon reflexes are more indicative of hypothyroidism rather than an overdose of levothyroxine.

Correct Answer: B

Rationale: Atenolol, a beta-blocker, is not typically associated with tachycardia. Instead, drug toxicity of Atenolol is more commonly linked to bradycardia due to its beta-blocking effects on the heart's electrical conduction system. Symptoms of Atenolol toxicity may include heart failure (CHF), AV block, and a sedative appearance, but not tachycardia.

Correct Answer: C

Rationale: Opioid analgesics like dextromethorphan and methadone are primarily used for pain management and cough suppression. Sedation is not a primary indication for these medications.

Correct Answer: B

Rationale: Prednisone toxicity is not typically associated with hypotension; instead, it can lead to hypertension. Cataracts, psychosis, and acne are known side effects of Prednisone toxicity.