A hydrophilic medicinal agent has the following property:

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: Hydrophilic agents have low ability to penetrate through cell membrane lipids due to their polar nature. Lipids are hydrophobic, causing repulsion. This prevents direct diffusion of hydrophilic molecules across the lipid bilayer. This leads to the correct answer, A. Summary of why other choices are incorrect: B: Endocytosis involves engulfing particles into cells, not typical for small hydrophilic molecules. C: The blood-brain barrier is selective and restricts the passage of hydrophilic substances. D: High reabsorption in renal tubules would apply to hydrophobic agents that can pass through lipid membranes easily, not hydrophilic agents.

Correct Answer: B

Rationale: The correct answer is B: Lidocaine. Lidocaine is a Class Ib antiarrhythmic agent that stabilizes cell membranes by blocking sodium channels, reducing excitability and conduction velocity in cardiac tissue. It is commonly used to treat ventricular arrhythmias. Cocaine (A) is a local anesthetic but not typically used as an antiarrhythmic. Bupivacaine (C) and Ropivacaine (D) are long-acting local anesthetics and are not commonly used as antiarrhythmics due to their mechanism of action.

Correct Answer: C

Rationale: Physostigmine is the correct answer for treating atropine intoxication due to its ability to cross the blood-brain barrier and inhibit acetylcholinesterase, increasing acetylcholine levels. Neostigmine (A) is primarily used for myasthenia gravis, Carbochol (B) is a non-selective cholinomimetic, and Lobeline (D) is a nicotinic receptor agonist.

Correct Answer: A

Rationale: The correct answer is A: Atracurium. Atracurium is preferred in patients with renal failure because it is metabolized by Hoffman elimination independent of renal or hepatic function. Succinylcholine (B) is not recommended in renal failure due to prolonged paralysis. Pipecuronium (C) and Doxacurium (D) are primarily eliminated by renal excretion, making them unsuitable for patients with renal failure.

Correct Answer: A

Rationale: Norepinephrine is a neurotransmitter that acts on alpha-adrenergic receptors causing vasoconstriction by stimulating smooth muscle contraction in blood vessels. This leads to increased blood pressure. Vasodilatation (B) is incorrect as norepinephrine does not cause blood vessels to dilate. Bronchodilation (C) is incorrect because norepinephrine primarily affects blood vessels, not bronchioles. Decreased potassium concentration in the plasma (D) is incorrect as norepinephrine does not directly impact potassium levels. Therefore, the correct answer is A: Vasoconstriction.