Action of i. v. thiopentone is terminated by ?
**Core Concept**
Thiopentone is a barbiturate anesthetic agent used for inducing general anesthesia. Its action is terminated by the metabolism process, specifically by an enzyme that rapidly inactivates the drug.
**Why the Correct Answer is Right**
The correct answer is related to the enzyme responsible for metabolizing thiopentone. Thiopentone is rapidly metabolized by the liver enzyme **cytochrome P450**, particularly **CYP2C9**, to an inactive metabolite. This rapid metabolism is responsible for the short duration of action of thiopentone. The enzyme quickly inactivates the drug, terminating its anesthetic effect.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because thiopentone is not primarily excreted by the kidneys. While some of the metabolites may be excreted by the kidneys, the primary mechanism of termination of thiopentone's action is not renal excretion.
**Option B:** This option is incorrect because thiopentone does not have a significant effect on the cytoskeleton. Its action is primarily related to its anesthetic effects on the central nervous system.
**Option C:** This option is incorrect because thiopentone does not have a significant role in the regulation of gene expression. Its action is primarily related to its anesthetic effects on the central nervous system.
**Clinical Pearl / High-Yield Fact**
One important clinical consideration is that thiopentone can cause a transient increase in intracranial pressure, particularly in patients with head injuries or increased intracranial pressure. This effect is due to its vasodilatory properties and should be kept in mind when using thiopentone for anesthesia in these patients.
**Correct Answer:** C.