Which one of the following groups is responsible for the potency and the toxicity of local anesthetics?

Correct Answer: C

Rationale: The correct answer is C: Lipophylic group. Local anesthetics exert their potency and toxicity by interacting with sodium channels in nerve fibers. The lipophilic group determines the lipid solubility of the anesthetic, affecting its ability to penetrate nerve membranes and block sodium channels. Ionizable groups are responsible for the drug's pH-dependent solubility and onset of action, while the intermediate chain contributes to the drug's duration of action. Choice D is incorrect because not all components (ionizable group and intermediate chain) solely determine potency and toxicity of local anesthetics.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Ipratropium is a bronchodilator used in asthma. 2. It works by blocking muscarinic receptors, reducing bronchoconstriction. 3. Atropine and Homatropine are anticholinergic drugs but not commonly used in asthma. 4. Lobeline is a respiratory stimulant, not used for bronchodilation in asthma. Summary: Ipratropium is the correct choice as it specifically targets bronchodilation in asthma by blocking muscarinic receptors. Atropine, Homatropine, and Lobeline are not commonly used for this purpose in asthma treatment.

Correct Answer: A

Rationale: The correct answer is A because alpha agonists cause mydriasis (pupil dilation), not miosis (pupil constriction). Alpha agonists like phenylephrine work by stimulating alpha receptors in the iris dilator muscle, leading to pupil dilation. Therefore, choice A is incorrect. Choices B, C, and D are incorrect because alpha agonists do cause mydriasis, beta antagonists do decrease the production of aqueous humor, and alpha agonists do increase the outflow of aqueous humor from the eye, respectively.

Correct Answer: C

Rationale: Rationale: 1. Pindolol is a non-selective beta-blocker with intrinsic sympathomimetic activity (partial beta-agonist). 2. It competes with catecholamines for beta-adrenergic receptors, reducing heart rate and blood pressure. 3. Propranolol (A) and metoprolol (B) are non-selective beta-blockers without partial agonist activity. 4. Betaxolol (D) is a selective beta-1 blocker without partial agonist activity. Summary: Pindolol (C) is the correct choice due to its partial beta-agonist activity, which distinguishes it from the other options that lack this property.

Correct Answer: B

Rationale: The correct answer is B: Triazolam. Triazolam has the shortest elimination half-life among the options provided, typically around 2-5 hours. This is due to its rapid metabolism and elimination from the body. In comparison, Temazepam (A) has a longer half-life of around 8-20 hours, Flurazepam (C) has a half-life of 40-250 hours, and Diazepam (D) has a half-life of 20-100 hours. Therefore, Triazolam is the best choice for short-term hypnotic effects due to its quick elimination from the body.