Which of the following drug(s) is/are mainly metabolized extra hepatically in plasma?
**Core Concept**
The question is testing the knowledge of extrahepatic metabolism of drugs in the plasma. Extrahepatic metabolism refers to the process by which drugs are metabolized outside the liver, primarily in the plasma or by other organs. This concept is crucial in pharmacology, as it helps in understanding the pharmacokinetics and pharmacodynamics of various drugs.
**Why the Correct Answer is Right**
Enzymes like cholinesterase, aminopeptidases, and carboxylesterases are responsible for the extrahepatic metabolism of certain drugs. For example, succinylcholine, a muscle relaxant, is metabolized by plasma cholinesterase. This enzyme catalyzes the hydrolysis of succinylcholine, leading to its inactivation. Other drugs like lidocaine and procainamide are also metabolized by plasma esterases.
**Why Each Wrong Option is Incorrect**
* **Option A:** (no information provided)
* **Option B:** (no information provided)
* **Option C:** (no information provided)
* **Option D:** (no information provided)
**Clinical Pearl / High-Yield Fact**
It's essential to remember that extrahepatic metabolism can significantly affect the pharmacokinetics and pharmacodynamics of certain drugs. This means that factors affecting plasma cholinesterase activity, such as genetic variations or certain diseases, can impact the efficacy and safety of drugs metabolized by this enzyme.
**Correct Answer: A. Succinylcholine**