In case of liver disorders accompanied by a decline in microsomal enzyme activity the duration of action of some drugs is:

Correct Answer: B

Rationale: 1. Liver disorders can lead to a decline in microsomal enzyme activity. 2. Microsomal enzymes play a role in drug metabolism. 3. Reduced enzyme activity can lead to decreased drug metabolism. 4. Decreased drug metabolism can result in an enlarged duration of action. 5. Therefore, in liver disorders, the duration of action of drugs is likely to be enlarged. Summary: A: Incorrect - Decreased duration of action is less likely due to reduced metabolism. C: Incorrect - Activity of microsomal enzymes affects drug metabolism. D: Incorrect - Changes in drug action may be significant due to altered metabolism.

Correct Answer: C

Rationale: Acetylcholine is not used in clinical practice because it is very rapidly hydrolyzed by the enzyme acetylcholinesterase. Upon administration, it quickly breaks down before exerting its desired effects. This rapid hydrolysis limits its therapeutic efficacy, making it unsuitable for clinical use. Other choices (A, B, D) are incorrect as acetylcholine's lack of use is primarily due to its rapid degradation, not its toxicity, high doses requirement, or costliness.

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.