The data shown in the table below concern the effects of drugs on transmitter function in the CNS. Which one of the drugs is most likely to alleviate extrapyramidal dysfunction caused by typical antipsychotics?

Correct Answer: C

Rationale: Typical antipsychotics block dopamine D2 receptors, causing extrapyramidal symptoms (EPS) like parkinsonism due to dopamine-acetylcholine imbalance in the basal ganglia. Drugs alleviating EPS often restore this balance. Drug A strongly activates dopamine receptors, mimicking dopamine and potentially countering the blockade, but excessive activation risks psychosis. Drug B moderately boosts dopamine and GABA, offering some benefit but less specificity. Drug C potently blocks muscarinic acetylcholine receptors, reducing cholinergic overactivity that emerges from dopamine depletion, a well-established approach (e.g., benztropine) for EPS relief without worsening psychosis. Drug D enhances GABA, unrelated to EPS mechanisms. Drug E mildly activates dopamine and GABA, insufficient for robust relief. Blocking muscarinic receptors directly addresses the cholinergic excess, making it the most effective and clinically validated strategy for EPS management.

Correct Answer: C

Rationale: Nitrous oxide has a high minimum alveolar concentration (MAC >100%), not low, due to low potency, so that's false. Halogenated agents (e.g., isoflurane) have higher brain:blood coefficients, reflecting solubility, making that false. They reduce mean arterial pressure (MAP) proportional to alveolar concentration via vasodilation, a true statement. Nitrous oxide does decrease tidal volume and increase respiratory rate, true. They don't reduce cerebral metabolic rate via blood flow alone but directly. MAP reduction is a key hemodynamic effect, guiding anesthetic depth monitoring.

Correct Answer: D

Rationale: Mean effective dose (ED50) affects 50% of a population, but individuals vary-some need more or less due to metabolism, weight, or genetics, a clinical reality. Severe side effects aren't 50%-that's toxicity. Ethnic differences influence response, but dose variation is broader. No effect in 50% misreads ED50. Dose adjustment reflects individual pharmacokinetics, key to practice.

Correct Answer: B

Rationale: In a patient with a hypertensive emergency, rapid and effective blood pressure reduction is crucial to prevent organ damage. The recommendation for IV administration of antihypertensive medications in this scenario is to titrate the medication to achieve a safe reduction in blood pressure, generally targeting a decrease in mean arterial pressure by no more than 25% within the first hour. The specific medication and infusion rate are dependent on the patient's clinical status and individual factors. Therefore, the maximum dose and duration of infusion must be tailored to the patient's response, with close monitoring by healthcare providers. Hence, determining a fixed time for the maximum dose of the drug to be infused is not appropriate in this critical care scenario.

Correct Answer: A

Rationale: While Propranolol is commonly used to treat conditions such as hypertension and certain heart-related issues, it is also used off-label for the treatment of post-traumatic stress disorder (PTSD). Propranolol has shown efficacy in reducing the intensity of emotional memories and symptoms associated with PTSD by blocking the effects of stress hormones. It is believed to help alleviate symptoms such as anxiety and hyperarousal in individuals with PTSD. However, it is important to note that the off-label use of Propranolol for PTSD should only be done under the guidance and supervision of a healthcare professional.