Question

Arrange the below listed anesthetic agents from lower to higher duration of action
(A) Amobarbitone
(B) Thiopentone
(C) Pentobarbitone
(D) Phenobarbitone
Choose the correct answer from the options given below:

• A. (B), (A), (C), (D).
• B. (B), (C), (A), (D).
• C. (B), (C), (D), (A).
• D. (C), (B), (D), (A).

Hint:

- Ultra-short acting = Thiopentone (B)
- Long acting = Phenobarbitone (D)
Placing B first and D last in the sequence allows you to quickly find the correct option.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Barbiturates are central nervous system depressants classified into different categories based on their lipid solubility and duration of action.
Detailed Explanation:
Let us analyze the duration of action of the listed barbiturates:
- (B) Thiopentone: An ultra-short-acting barbiturate. Because of its extremely high lipid solubility, it crosses the blood-brain barrier rapidly and is then redistributed into fat and muscle, terminating its action within $5$-$15$ minutes. This is the shortest duration.
- (C) Pentobarbitone: A short-to-intermediate-acting barbiturate. It is used as a general anesthetic or euthanasia agent in veterinary practice, with a duration of action of $1$-$2$ hours.
- (A) Amobarbitone: An intermediate-acting barbiturate, with a duration of action ranging from $3$-$6$ hours.
- (D) Phenobarbitone: A long-acting barbiturate. It has low lipid solubility and is slowly metabolized, with an active duration exceeding $8$-$12$ hours. It is primarily used as an anticonvulsant.
Arranging these from shortest (lower) to longest (higher) duration of action:
\[ \text{Thiopentone (B)} \rightarrow \text{Pentobarbitone (C)} \rightarrow \text{Amobarbitone (A)} \rightarrow \text{Phenobarbitone (D)} \] This corresponds to the sequence: (B), (C), (A), (D).

Step 2: Final Answer:
The correct sequential arrangement corresponds to Option (B).