What is true about the sensitivity of nerve fibres to local anaesthetics?

Correct Answer: A

Rationale: In pharmacology, understanding the sensitivity of nerve fibers to local anesthetics is crucial for effective clinical practice. The correct answer, A) Small fibers are more sensitive, is supported by the fact that smaller diameter nerve fibers have a higher surface area-to-volume ratio, making them more susceptible to the effects of local anesthetics. These small fibers, which are responsible for transmitting pain and temperature sensations, are blocked more readily by local anesthetics compared to larger fibers. Option B) Large fibers are more sensitive, is incorrect because larger fibers have a lower surface area-to-volume ratio, making them less sensitive to local anesthetics. These fibers primarily carry touch and proprioception information and are less affected by local anesthetics. Option C) Both small and large fibers are equally sensitive, is incorrect as the differences in surface area-to-volume ratio between small and large fibers dictate their sensitivity to local anesthetics. Option D) Small fibers are resistant, is also incorrect as small fibers are actually more sensitive to local anesthetics due to their physiological characteristics. In an educational context, understanding the differential sensitivity of nerve fibers to local anesthetics is crucial for tailoring drug therapies for specific conditions. This knowledge helps healthcare professionals in selecting the appropriate local anesthetic agent and dosage based on the desired clinical outcome and the type of nerve fibers involved.

Correct Answer: C

Rationale: In this Pharmacology CNS Drugs Quiz question, the correct answer is C) Vigabatrin. Vigabatrin is an irreversible inhibitor of GABA transaminase, an enzyme responsible for breaking down GABA (gamma-aminobutyric acid) in the brain. By inhibiting this enzyme, Vigabatrin increases the levels of GABA in the brain, leading to enhanced GABAergic neurotransmission and ultimately reducing neuronal excitability. Option A) Pyrimidine is incorrect because it is a class of organic compounds and not a specific drug used as an irreversible inhibitor of GABA transaminase. Option B) Lamotrigine is incorrect because it is an anticonvulsant medication that works by inhibiting voltage-gated sodium channels, not by inhibiting GABA transaminase. Option D) Gabapentin is incorrect because it is a structural analog of GABA, but it does not directly inhibit GABA transaminase. Understanding the mechanism of action of CNS drugs, such as GABAergic agents like Vigabatrin, is crucial for healthcare professionals in managing patients with epilepsy and other neurological disorders. By grasping how different drugs interact with specific targets in the brain, healthcare providers can make informed decisions about drug selection, dosing, and monitoring to optimize patient outcomes.

Correct Answer: A

Rationale: In pharmacology, particularly when studying CNS drugs, understanding the Fenton reaction is crucial as it relates to oxidative stress and neurotoxicity. The correct answer is A) Free radical. The Fenton reaction involves the generation of hydroxyl radicals (·OH) through the reaction between hydrogen peroxide (H2O2) and transition metals like iron (Fe). These highly reactive free radicals can cause damage to cellular components in the CNS, leading to neurodegeneration and other harmful effects. Option B) Hydrogen peroxide is incorrect because although it is involved in the Fenton reaction, it is not the end product but rather a precursor to the formation of more reactive free radicals like hydroxyl radicals. Option C) Nitric oxide is incorrect as it is a signaling molecule in the CNS and not directly related to the Fenton reaction or the generation of free radicals through oxidative stress. Understanding the Fenton reaction in the context of CNS pharmacology is important for students to grasp the mechanisms underlying drug-induced neurotoxicity and the role of oxidative stress in CNS disorders. By knowing how free radicals are generated and their impact on neuronal cells, students can appreciate the importance of antioxidant therapies in mitigating neurodegenerative processes and developing safer CNS drugs.

Correct Answer: C

Rationale: In pharmacology, the correct answer to the question "Which loop diuretic is more likely to have oto toxicity?" is C) Ethacrynic acid. Ethacrynic acid is more likely to cause oto toxicity compared to other loop diuretics due to its non-sulfonamide structure, making it a potential alternative for patients who are allergic to sulfonamide medications like furosemide, bumetanide, and torsemide. Furosemide (A), bumetanide (B), and torsemide (D) are all sulfonamide loop diuretics, which are less likely to cause oto toxicity compared to ethacrynic acid. It is important for pharmacology students to understand the differences in drug structures and their potential side effects to make informed clinical decisions. Educationally, this question highlights the importance of understanding the unique characteristics of different medications within the same class to optimize patient care and minimize adverse effects. By knowing the specific side effect profiles of loop diuretics, healthcare professionals can select the most appropriate drug for individual patients based on their medical history and drug allergies.

Correct Answer: A

Rationale: Rationale: Lithium toxicity may manifest as polyuria because lithium is a mood-stabilizing drug commonly used to treat bipolar disorder. One of lithium's primary side effects is its impact on the kidneys, leading to decreased ability to concentrate urine, resulting in increased urine output (polyuria). This occurs due to lithium interfering with the action of antidiuretic hormone in the kidneys. Option B, nephrotic syndrome, is incorrect because lithium toxicity does not typically lead to the characteristic symptoms of nephrotic syndrome such as proteinuria, edema, and hypoalbuminemia. Option C, renal calculi, is incorrect because although long-term lithium use can increase the risk of developing kidney stones, it is not a typical manifestation of acute lithium toxicity. Option D, acute renal failure, is incorrect because while severe lithium toxicity can lead to renal failure in extreme cases, polyuria is more characteristic of early signs of lithium toxicity. Educational Context: Understanding the manifestations of lithium toxicity is crucial for healthcare providers managing patients on lithium therapy. Recognizing the signs and symptoms of lithium toxicity, such as polyuria, early can prevent serious complications and guide appropriate interventions. Educating patients on the importance of regular monitoring and reporting of symptoms to their healthcare provider is essential in managing their lithium therapy effectively.