Parenteral administration:

Correct Answer: C

Rationale: Parenteral administration usually produces a more rapid response than oral administration because the medication bypasses the digestive system and is directly absorbed into the bloodstream. This route includes injections, intravenous infusions, and intramuscular injections, allowing for quicker onset of action. Option A is incorrect as parenteral administration can be used in unconscious patients. Option B is incorrect as parenteral administration can provide more accurate dosages. Option D is incorrect as parenteral administration is actually preferred in emergency situations due to its rapid effects.

Correct Answer: B

Rationale: The correct answer is B: Tetracaine. Tetracaine is a long-acting local anesthetic commonly used for regional nerve block anesthesia due to its duration of action. It provides effective and prolonged pain relief in a specific area by blocking nerve conduction. Procaine (A) is a short-acting local anesthetic, making it less suitable for regional nerve block anesthesia. Bupivacaine (D) is a long-acting local anesthetic like tetracaine, but it is more commonly used for epidural or spinal anesthesia rather than regional nerve blocks. Therefore, tetracaine is the most appropriate choice for regional nerve block anesthesia among the options provided.

Correct Answer: A

Rationale: The correct answer is A: Scopolamine. Scopolamine is a muscarinic receptor-blocking drug that antagonizes the action of acetylcholine at muscarinic receptors. Scopolamine is commonly used for its anticholinergic effects, such as reducing salivation and mucous secretion. B: Pipecuronium is a neuromuscular blocking agent that acts at the neuromuscular junction, not at muscarinic receptors. C: Trimethaphan is a ganglionic blocker that acts at the autonomic ganglia, not at muscarinic receptors. D: Pilocarpine is a muscarinic receptor agonist, not a muscarinic receptor blocker. It is used to stimulate muscarinic receptors for various therapeutic purposes.

Correct Answer: C

Rationale: The correct answer is C (Pancuronium). Pancuronium is a non-depolarizing neuromuscular blocker that can cause tachycardia by blocking muscarinic receptors leading to the inhibition of the parasympathetic system. This results in the dominance of the sympathetic system, leading to tachycardia. Tubocurarine (A) and Atracurium (B) are also non-depolarizing neuromuscular blockers, but they do not directly cause tachycardia. Succinylcholine (D) is a depolarizing neuromuscular blocker that can cause bradycardia due to its effects on acetylcholine receptors at the neuromuscular junction.

Correct Answer: D

Rationale: The correct answer is D because ephedrine actually increases arterial pressure by stimulating alpha-adrenergic receptors, leading to vasoconstriction. A is incorrect as ephedrine works by directly stimulating adrenergic receptors, not by releasing stored catecholamines. B is correct as ephedrine is indeed a mild CNS stimulant. C is incorrect as tachyphylaxis, or a rapid decrease in response with repeated administration, is not commonly associated with ephedrine.