The nurse is reviewing the classes of antidysrhythmic drugs. Amiodarone (Cordarone) is classified on the Vaughan Williams classification as a class III drug, which means it works by which mechanism of action?

Correct Answer: B

Rationale: The correct answer is B because Amiodarone (Cordarone) is classified as a class III antidysrhythmic drug which acts by prolonging the action potential duration. This leads to prolongation of the refractory period of the heart, helping to prevent reentry of arrhythmias. Choice A is incorrect as blocking slow calcium channels is the mechanism of action for class IV drugs. Choice C is incorrect as blocking sodium channels is the mechanism for class I drugs. Choice D is incorrect as decreasing spontaneous depolarization is the mechanism for class II drugs.

Correct Answer: B

Rationale: The correct answer is B because absorption of drugs taken orally depends on the secretion and motor function of the gastrointestinal (GI) tract. This is because the drug needs to be properly broken down and absorbed through the GI tract before entering the bloodstream. Other choices are incorrect because: A: Fast onset of effect is more characteristic of routes like intravenous or inhalation. C: A drug reaching the blood passing the liver is more characteristic of the hepatic first-pass effect, not specific to the oral route. D: Sterilization of medicinal forms is not obligatory for the oral route, as proper storage and handling can ensure safety.

Correct Answer: B

Rationale: The correct answer is B: Cumulative effect. Continuous or repeated intake of a drug can lead to the accumulation of the drug in the body, causing a higher concentration than intended, leading to toxic reactions. Refractoriness (A) refers to decreased response to a drug over time. Tolerance (C) is the need for higher doses to achieve the same effect, not necessarily leading to toxicity. Tachyphylaxis (D) is a rapid decrease in response to a drug with repeated administration, not directly related to toxicity.

Correct Answer: D

Rationale: The correct answer is D because a vasoconstrictor actually enhances the effects of a local anesthetic by reducing its uptake by the surrounding nerves. This helps to prolong the duration of action of the anesthetic. Choices A and B are incorrect because a vasoconstrictor can retard drug removal from the injection site, which can increase the chance of toxicity. Choice C is incorrect because a vasoconstrictor actually decreases blood levels by constricting blood vessels at the site of administration, which can lead to localized effects.

Correct Answer: D

Rationale: The correct answer is D because ganglion-blockers (A) and neuromuscular junction blockers (C) both belong to the group of nicotinic receptor-blocking drugs. Ganglion-blockers act on nicotinic receptors in autonomic ganglia, while neuromuscular junction blockers act on nicotinic receptors at the neuromuscular junction. Atropine-similar drugs (B) do not directly block nicotinic receptors, so they are not part of this particular group of drugs. Therefore, choices A and C cover all the drugs that block nicotinic receptors, making D the correct answer.