This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Which of the following drugs is contra-indicated in acute intermittent porphyria? 
Select and explain. 
A. Thiopentone, B. Midazolam, C. Propofol, D. Etomidate
A: Thiopentone
Answer: A: Thiopentone 
Explanation: Barbiturates are contra-indicated in acute intermittent porphyria. Ref: KD Tripathi 8th ed.