**Question:** Drug used in Acute Intermittent Porphyria is

A. Carbamazepine
B. Phenobarbital
C. Phenytoin
D. Valproic acid

**Correct Answer:** D. Valproic acid

**Core Concept:**
Acute Intermittent Porphyria (AIP) is a genetically inherited disorder affecting the heme synthesis pathway. It leads to a deficiency in the enzyme delta-aminolevulinic acid dehydratase, which results in increased levels of aminolevulinic acid and porphobilinogen. These elevated levels can cause severe abdominal pain, neuropathy, and neuropsychiatric symptoms.

**Why the Correct Answer is Right:**
Valproic acid (D) is a commonly used anticonvulsant that has been found to be effective in managing acute attacks of AIP. It works by inhibiting the production of porphobilinogen and aminolevulinic acid from delta-aminolevulinic acid in the heme synthesis pathway. By doing so, it effectively reduces the levels of these toxic substances and alleviates the symptoms associated with AIP attacks.

**Why Each Wrong Option is Incorrect:**

A. Carbamazepine (A) is an anticonvulsant, but it is not specifically used for AIP. It is primarily effective in managing epilepsy and bipolar disorder.

B. Phenobarbital (B) is another anticonvulsant, but it has less efficacy compared to valproic acid in managing AIP attacks.

C. Phenytoin (C) is an anticonvulsant, but it is less effective than valproic acid in controlling AIP symptoms.

**Clinical Pearl:**
The management of AIP should involve prophylactic treatment with valproic acid to prevent frequent attacks. In acute attacks, intravenous administration of hydroxocobalamin (vitamin B12) can be considered as it binds to the excess porphobilinogen and aminolevulinic acid, reducing their toxicity. However, valproic acid remains the first-line treatment for AIP management.