## **Core Concept**
Isoniazid is a first-line antitubercular medication that can cause severe toxicity, including seizures and metabolic acidosis, when taken in overdose. The treatment of isoniazid poisoning involves administering specific antidotes that can counteract its toxic effects. Understanding the mechanism of isoniazid toxicity and its antidotes is crucial for managing such cases.

## **Why the Correct Answer is Right**
The correct answer involves the use of pyridoxine (Vitamin B6) as an antidote in isoniazid poisoning. Isoniazid acts by forming a hydrazone with pyridoxal phosphate, which is a cofactor for the enzyme glutamic acid decarboxylase (GAD). This results in a decrease in the synthesis of the neurotransmitter GABA, leading to seizures. **Pyridoxine** replenishes pyridoxal phosphate, thereby helping to restore GABA synthesis and mitigating the risk of seizures. This is a critical intervention in the management of isoniazid overdose.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While supportive care and monitoring are crucial in managing isoniazid poisoning, this option does not specify an antidote.
- **Option B:** Activated charcoal may be useful in preventing absorption of the drug if administered early after ingestion, but it is not specific for treating isoniazid toxicity.
- **Option C:** Although diazepam can be used to control seizures caused by isoniazid, it does not address the underlying biochemical defect and is considered adjunctive therapy.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **pyridoxine (Vitamin B6)** is a specific antidote for isoniazid-induced seizures and should be administered in cases of suspected isoniazid overdose, especially if seizures are present or anticipated. The dose of pyridoxine often matches the dose of isoniazid ingested.

## **Correct Answer:** . Pyridoxine.