Indicate the local anesthetic agent, which has a shorter duration of action:

Correct Answer: B

Rationale: The correct answer is B: Procaine. Procaine has a shorter duration of action compared to the other choices. This is because procaine is an ester-type local anesthetic, which undergoes rapid hydrolysis by plasma cholinesterase, resulting in a shorter duration of action. In contrast, lidocaine, bupivacaine, and ropivacaine are amide-type local anesthetics, which are metabolized more slowly, leading to longer durations of action. Therefore, procaine is the local anesthetic with the shortest duration among the options provided.

Correct Answer: C

Rationale: Certainly! The correct answer is C: Homatropine. Homatropine is an antimuscarinic drug that works by blocking muscarinic receptors in the eye, causing dilation of the pupil (mydriasis). This effect is useful in ophthalmology for procedures requiring dilation of the pupil for examination or surgery. Now, let's analyze why the other choices are incorrect: A: Pilocarpine is a muscarinic agonist that constricts the pupil. B: Neostigmine is an acetylcholinesterase inhibitor used to increase muscle contractions. D: Ipratropium is an anticholinergic drug primarily used for bronchodilation in conditions like asthma and COPD. In summary, Homatropine is the correct choice as it is the antimuscarinic drug used for mydriasis, while the other options have different mechanisms of action and purposes.

Correct Answer: B

Rationale: Correct Answer: B (Increase peripheral arterial resistance) Rationale: Nonselective beta receptor agonists stimulate beta-1 and beta-2 receptors. Activation of beta-1 receptors on the heart increases cardiac output (A). Activation of beta-2 receptors in peripheral arteries causes vasodilation, leading to a decrease in peripheral arterial resistance (C). Mean arterial pressure is determined by cardiac output and peripheral resistance, so decreasing peripheral resistance would not directly lead to a decrease in the mean pressure (D). Therefore, the correct answer is B because nonselective beta receptor agonists do not increase peripheral arterial resistance.

Correct Answer: D

Rationale: The correct answer is D: Butoxamine. Butoxamine is a beta2-selective antagonist due to its high affinity for beta2-adreagent receptors over beta1 receptors. This selectivity allows it to block the effects of beta2 activation specifically. Tolazoline (A) is an alpha-adrenergic antagonist, Pindolol (B) is a non-selective beta-blocker, and Ergotamine (C) is a serotonin receptor agonist. Therefore, they are not beta2-selective antagonists.

Correct Answer: C

Rationale: The correct answer is C: Phenobarbital. Phenobarbital has a longer elimination half-life of 4-5 days due to its extensive hepatic metabolism and slow excretion. Secobarbital (A) has a shorter half-life around 15 hours. Thiopental (B) has a very short half-life of 5-10 hours. Amobarbital (D) has a half-life of around 10-25 hours, making it shorter than phenobarbital. Therefore, based on the pharmacokinetics of these drugs, phenobarbital is the most likely choice with a 4-5 days elimination half-life.