Question

Given below are two statements:
Statement (I) : Permethrin is a Type I pyrethroid
Statement (II) : Deltamethrin and cypermethrin are Type II pyrethroid
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Type II pyrethroids have a cyano group. You can remember this because the names of most Type II pyrethroids (like Cypermethrin, Deltamethrin, Fenvalerate) contain a "C" or "D", while Type I pyrethroids (like Permethrin, Allethrin) do not.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Synthetic pyrethroids are insecticides modeled after natural pyrethrins.
They are classified into Type I and Type II based on their chemical structure (specifically the presence or absence of an alpha-cyano group) and their neurotoxic mechanism of action.
Detailed Explanation:
Let us evaluate the statements:
- Statement (I) analysis: Type I pyrethroids lack an alpha-cyano group. They delay the closure of voltage-gated sodium channels, causing repetitive neuronal discharges (known as the "T-syndrome"). Permethrin is a classic Type I pyrethroid. Thus, Statement (I) is correct.
- Statement (II) analysis: Type II pyrethroids possess an alpha-cyano group at the phenoxybenzyl alcohol position. They cause much longer delays in sodium channel inactivation, leading to persistent depolarization and a "CS-syndrome" (choreoathetosis/salivation). Deltamethrin and cypermethrin are classic Type II pyrethroids. Thus, Statement (II) is correct.

Step 2: Final Answer:
Since both Statement (I) and Statement (II) are correct, the correct choice is Option (A).