Which of the following agents is an alfa2-selective agonist with ability to promote constriction of the nasal mucosa?

Correct Answer: A

Rationale: The correct answer is A: Xylometazoline. Xylometazoline is an alpha2-selective agonist, which means it specifically targets alpha2-adrenergic receptors. By activating these receptors, xylometazoline promotes constriction of the nasal mucosa, leading to reduced swelling and congestion. Phenylephrine (B) and methoxamine (C) are alpha1-selective agonists, not alpha2-selective, so they would not promote constriction of nasal mucosa. Epinephrine (D) is a non-selective agonist that acts on both alpha and beta receptors, leading to a broader range of effects, not specifically nasal constriction.

Correct Answer: C

Rationale: During slow wave sleep (stage 3 and 4 NREM sleep), somnambulism (sleepwalking) and nightmares occur. This is because these stages are characterized by deep sleep, where the brain activity is at its lowest, making it more likely for these types of sleep disturbances to happen. Choice A is incorrect because dreams primarily occur during REM sleep, not slow wave sleep. Choice B is incorrect as the secretion of adrenal steroids typically peaks in the early morning, not during slow wave sleep. Choice D is incorrect as the secretion of somatotropin (growth hormone) is actually at its highest during slow wave sleep, aiding in physical growth and repair.

Correct Answer: A

Rationale: The correct answer is A: Tolerance. Benzodiazepines are known to lead to tolerance, meaning that over time, the body requires higher doses to achieve the same effect. This limits their usefulness as long-term treatment options. Atropine-like symptoms (B) are not associated with benzodiazepines. Psychotic episodes (C) and myasthenic syndrome (D) are also not common side effects of benzodiazepines. Therefore, the correct answer is A as tolerance limits the effectiveness of benzodiazepines over time.

Correct Answer: C

Rationale: The correct answer is C: Mu-receptors. Mu-receptors are responsible for euphoria and respiratory depression because they are primarily involved in the analgesic effects and central nervous system depression associated with opioids. Kappa-receptors (choice A) are more related to analgesia and sedation. Delta-receptors (choice B) are also involved in analgesia but to a lesser extent compared to Mu-receptors. Choice D is incorrect as not all opioid receptors are responsible for euphoria and respiratory depression.

Correct Answer: C

Rationale: Certainly! The correct answer is C: Alcohol dehydrogenase. Fomepizole is used in treating methanol and ethylene glycol toxicity by inhibiting alcohol dehydrogenase, preventing the formation of toxic metabolites. This mechanism blocks the conversion of methanol and ethylene glycol into their toxic byproducts, formic acid, and glycolic acid, respectively. Choices A, B, and D are incorrect as fomepizole does not target aldehyde dehydrogenase, acetylcholinesterase, or monoamine oxidase in this context.