Question

Arrange the below listed sulphonamides in the sequence from short to long duration of action:
(A). Sulphadimidine
(B). Sulphadoxine
(C). Sulphadiazine
(D). Sulphadimethoxine
Choose the correct answer from the options given below:

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

Hint:

To remember the duration of action for sulfonamides:
- Sulphadiazine is short-acting.
- Sulphadoxine is ultra-long-acting (often used in long-lasting combinations).
- Dimethoxine is longer-acting than dimidine.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Sulfonamides are synthetic antimicrobial agents that inhibit bacterial folate synthesis by competing with para-aminobenzoic acid (PABA).
They are classified based on their pharmacokinetic properties, particularly their elimination half-life and duration of action in the body.

Step 2: Detailed Explanation:
Let us analyze the duration of action of the listed sulfonamides:
- Sulphadiazine (C): This is a rapid-acting, short-duration sulfonamide with a rapid elimination rate.
Its half-life is short, requiring frequent dosing to maintain therapeutic blood levels.
- Sulphadimidine (A): Also known as sulfamethazine, this is an intermediate-duration sulfonamide with a moderate elimination rate.
- Sulphadimethoxine (D): This is a long-acting sulfonamide.
It undergoes high renal tubular reabsorption and exhibits high plasma protein binding, which prolongs its presence in the body.
- Sulphadoxine (B): This is an ultra-long-acting sulfonamide.
It has an exceptionally long half-life and is often combined with pyrimethamine to provide long-lasting antimicrobial or antiprotozoal effects.
Arranging these sulfonamides from shortest to longest duration of action gives:
\[ \text{Sulphadiazine (C)} \rightarrow \text{Sulphadimidine (A)} \rightarrow \text{Sulphadimethoxine (D)} \rightarrow \text{Sulphadoxine (B)} \]

Step 3: Final Answer:
The correct sequential order from short to long duration of action is (C), (A), (D), (B). This corresponds to option (A).