Thiopentone is C/I in
**Question:** Thiopentone is C/I in
A. Enzyme systems
B. Central nervous system
C. Cardiovascular system
D. Limbic system
**Correct Answer:** C. Cardiovascular system
**Core Concept:** Thiopentone is a barbiturate drug with central nervous system depressant effects. It acts as a competitive inhibitor of enzymes involved in the synthesis of purines and pyrimidines, particularly enzymes in the deoxyribonucleotide synthesis pathway.
**Why the Correct Answer is Right:** Thiopentone primarily affects the cardiovascular system due to its action on the central nervous system (CNS). Inhibition of enzymes involved in purine and pyrimidine synthesis leads to decreased DNA and RNA synthesis, which results in CNS depression. This depression can manifest as sedation, unconsciousness, and eventually, respiratory and cardiovascular depression.
**Why Each Wrong Option is Incorrect:**
A. Enzyme systems: While thiopentone does inhibit enzymes involved in purine and pyrimidine synthesis, this is not the primary mechanism of action. The drug primarily affects the cardiovascular system through CNS depression.
B. Central nervous system: Although thiopentone does have effects on the CNS, the cardiovascular system is more directly affected due to the drug's impact on the CNS.
D. Limbic system: The limbic system is part of the CNS, but the cardiovascular system is more directly affected due to the drug's impact on the CNS.
**Clinical Pearl:** Thiopentone is used as an anesthetic agent due to its CNS depressant effects, which can lead to cardiovascular depression. Understanding the drug's pharmacology helps predict and manage its side effects, ensuring safe administration of the drug in clinical practice.