The amount of vasoconstrictor in 1 ml of 2% Lignocaine solution with 1:2,00,000 adrenaline is:
**Core Concept**
The question requires understanding of the concentration of vasoconstrictors in local anesthetic solutions, specifically the amount of adrenaline (epinephrine) in a 2% lignocaine solution with a 1:200,000 concentration.
**Why the Correct Answer is Right**
The correct answer is based on the calculation of the total volume of the solution. Since the solution is 2% lignocaine with 1:200,000 adrenaline, we can calculate the amount of adrenaline in 1 ml of the solution. A 1:200,000 concentration means that for every 1 ml of solution, there are 0.0005 mg (1/200,000) of adrenaline. Therefore, in 1 ml of 2% lignocaine solution, there is 0.0005 mg of adrenaline.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not provide a specific concentration or calculation for the amount of adrenaline in 1 ml of the solution.
* **Option B:** This option is incorrect because it is a random number without any basis in the calculation or concentration of the solution.
* **Option C:** This option is incorrect because it does not provide a correct calculation or concentration for the amount of adrenaline in 1 ml of the solution.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the concentration of vasoconstrictors in local anesthetic solutions can affect the duration of action and the risk of toxicity. Adrenaline, in particular, can cause vasoconstriction, which can increase the duration of action of the local anesthetic.
**Correct Answer:** 0.0005 mg.