A small amount of the volume of distribution is common for lipophylic substances easy penetrating through barriers and widely distributing in plasma, interstitial and cell fluids:

Correct Answer: B

Rationale: Rationale: B is correct because lipophilic substances have high affinity for fats and are able to penetrate barriers easily. However, a small volume of distribution indicates that these substances are mainly confined to the plasma and do not distribute widely into interstitial and cell fluids. Summary: A is incorrect because a small volume of distribution indicates limited distribution, not widespread distribution as stated. C is incorrect as there is a correct answer. D is incorrect as not all choices are correct, only B is accurate based on the characteristics of lipophilic substances.

Correct Answer: C

Rationale: The correct answer is C: Procaine does not readily penetrate the skin and mucosa. This is because procaine is a local anesthetic with poor lipid solubility, making it less able to penetrate through skin and mucosa efficiently. The other choices are incorrect because: A is correct as procaine contains an ester linkage; B is correct as procaine's metabolic product para-aminobenzoic acid can inhibit sulfonamide action; and D is correct as procaine is relatively short-acting compared to other local anesthetics like lidocaine. Therefore, C is the correct answer as it does not align with the properties of procaine.

Correct Answer: C

Rationale: Rationale: Scopolamine is effective for vestibular disturbances due to its central anticholinergic effects. It crosses the blood-brain barrier and blocks muscarinic receptors in the vestibular nuclei, helping to alleviate motion sickness. Atropine (A) mainly affects peripheral muscarinic receptors, not as effective. Ipratropium (B) is a bronchodilator, not used for motion sickness. Homatropine (D) is primarily used for ophthalmic purposes, not vestibular issues. Therefore, C is the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Epinephrine is not synthesized in the nerve endings. It is produced in the adrenal medulla and released into the bloodstream in response to stress. It travels through the blood to target tissues where it interacts with adrenoreceptors, leading to various physiological responses. Epinephrine does not directly interact with nerve endings for synthesis or action. Choices A, C, and D are incorrect because epinephrine is indeed synthesized in the adrenal medulla, transported in the blood to target tissues, and directly interacts with and activates adrenoreceptors, respectively.

Correct Answer: B

Rationale: Rationale: 1. Xylometazoline is an alpha2-selective agonist, which means it selectively activates alpha2 adrenergic receptors. 2. This action leads to vasoconstriction and reduces nasal congestion without affecting blood pressure. 3. Phenylephrine (choice A) is an alpha1-selective agonist, causing increased blood pressure. 4. Ephedrine (choice C) is a mixed agonist affecting both alpha and beta receptors. 5. Epinephrine (choice D) is a non-selective agonist acting on both alpha and beta receptors.