This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Seedatives & Hyponotics, Subject name: Pharmacology
In which of the following disorders, administration of barbiturates is contraindicated? 
Select and explain. 
A. Anxiety disorders, B. Acute intermittent porphyria, C. Kernicterus, D. Refractory status epilepticus
B: Acute intermittent porphyria
Answer: B: Acute intermittent porphyria 
Explanation: Ans. (B) Acute intermittent porphyria(Ref: KDT 8/e p427)Barbiturates induce the rate limiting enzyme 'd-aminolaevulanic acid synthase' in porphyrin synthesis. This increased synthesis of porphyrins can precipitate acute attack of AIP.