Which statement about lignocaine is correct?

Correct Answer: C

Rationale: In pharmacology, understanding the mechanism of action of drugs is crucial for safe and effective clinical practice. In the case of lignocaine (lidocaine), the correct statement is C) "Has higher affinity for activated than resting sodium channels." This statement is correct because lignocaine preferentially binds to and blocks activated sodium channels, which are channels that have opened in response to a depolarizing stimulus. By binding to these channels, lignocaine can inhibit the influx of sodium ions, thereby blocking the generation and conduction of action potentials along nerve fibers. This action results in local anesthesia. Now, let's examine why the other options are incorrect: A) Lignocaine penetrates the axon in its uncharged form, not charged form. Once inside the axon, it can become charged and exert its pharmacological effects. B) Bupivacaine is actually more potent than lignocaine, not the other way around. D) Lignocaine is an amide-type local anesthetic, not a weak acid. Educational context: Understanding the nuances of how local anesthetics like lignocaine work at the molecular level is essential for healthcare professionals who administer these drugs. Knowing that lignocaine targets activated sodium channels specifically can help in clinical decision-making, dosing optimization, and managing potential side effects related to its mechanism of action.

Correct Answer: C

Rationale: In this scenario, the correct medication to be maintained at the current dose for the 79-year-old man with Alzheimer's disease and elevated liver function tests is Rivastigmine (Option C). Rivastigmine is a cholinesterase inhibitor commonly used in Alzheimer's disease. Unlike other cholinesterase inhibitors like Donepezil (Option A), Galantamine (Option B), and Tacrine (Option D), Rivastigmine has a lower risk of hepatotoxicity and is less likely to exacerbate liver function abnormalities. This is due to its metabolism pathway, which involves minimal hepatic processing compared to the other medications listed. For educational context, it is crucial to understand the pharmacokinetics and potential adverse effects of medications used in Alzheimer's disease treatment. Considering a patient's comorbidities, such as liver dysfunction in this case, is vital in selecting appropriate medications to avoid further harm or complications. Pharmacovigilance and individualized treatment plans are essential in managing elderly patients with complex medical conditions like Alzheimer's disease and liver function abnormalities.

Correct Answer: D

Rationale: The correct answer is D) Physostigmine. Physostigmine is a cholinesterase inhibitor that can effectively lower intraocular pressure in open-angle glaucoma. Unlike the other options, physostigmine is known to cross the blood-brain barrier better due to its tertiary amine structure, allowing it to have effects in the central nervous system as well. A) Echothiophate is an irreversible cholinesterase inhibitor used topically to treat glaucoma but does not have significant blood-brain barrier penetration. B) Edrophonium is a short-acting cholinesterase inhibitor used for diagnostic purposes in myasthenia gravis and does not have significant blood-brain barrier penetration. C) Neostigmine is a cholinesterase inhibitor primarily used to treat myasthenia gravis and postoperative ileus, with minimal central nervous system effects due to poor blood-brain barrier penetration. Understanding the pharmacokinetic properties of CNS drugs is crucial for healthcare professionals to make informed decisions when selecting appropriate treatments for patients. Physostigmine's ability to cross the blood-brain barrier makes it a valuable option for conditions where central nervous system effects are desired.

Correct Answer: B

Rationale: The correct answer is B) Cholinergic transmission. Anticholinesterase inhibitors work by inhibiting the enzyme acetylcholinesterase, which is responsible for breaking down acetylcholine. By inhibiting this enzyme, the levels of acetylcholine increase in the synapses, leading to enhanced cholinergic transmission. This increased cholinergic activity can result in side effects such as nausea, vomiting, diarrhea, and muscle cramps due to the overstimulation of cholinergic receptors in various organs. Option A) Adrenergic transmission is incorrect because anticholinesterase inhibitors primarily affect cholinergic transmission, not adrenergic pathways. Option C) Purine metabolism impairment is incorrect as it is not directly related to the mechanism of action of anticholinesterase inhibitors. Option D) Transaminase enzyme elevation is incorrect as it pertains to liver function and enzyme levels, which are not directly impacted by anticholinesterase inhibitors. Educationally, understanding the mechanism of action of CNS drugs like anticholinesterase inhibitors is crucial for healthcare providers to predict and manage potential side effects in patients. By grasping how these drugs interact with neurotransmitter systems, practitioners can make informed decisions about treatment regimens and monitor patients effectively.

Correct Answer: B

Rationale: In this scenario, the most likely abnormality to be noted on the 24-h sleep study for the 38-year-old man with chronic anxiety and agitation who is being treated with a long-acting benzodiazepine would be "B) Hourly awakening from sleep." Explanation: - Benzodiazepines, especially long-acting ones, can disrupt normal sleep architecture by causing frequent awakenings during the night. This leads to a fragmented and poor-quality sleep pattern. - The individual may experience difficulty in maintaining continuous sleep due to the sedative effects of the benzodiazepine, resulting in frequent arousals throughout the night. - Hourly awakenings from sleep can contribute to sleep fragmentation, leading to non-restorative sleep and daytime drowsiness, which can exacerbate the existing issues of anxiety and agitation. Why other options are incorrect: - A) Calming effect during sleep induction: While benzodiazepines can have a calming effect when initiating sleep, the issue here pertains to maintaining sleep throughout the night. - C) Hypnotic effect with dreams: This option does not directly address the issue of frequent awakenings during sleep, which is the primary concern in this case. - D) Improved slow-wave sleep: Benzodiazepines are known to suppress slow-wave sleep, so this option is unlikely to be the abnormality noted in the sleep study. Educational context: Understanding the side effects of CNS drugs like benzodiazepines on sleep architecture is crucial for healthcare professionals managing patients with anxiety and sleep disturbances. Monitoring sleep patterns through studies like polysomnography can provide valuable insights into the impact of medications on sleep quality and guide treatment modifications to improve overall patient outcomes.