Which antidote is specifically indicated for isoniazid toxicity?

Pyridoxine, also known as vitamin B6, is the antidote specifically indicated for isoniazid toxicity. Isoniazid is an antibiotic commonly used to treat tuberculosis, but in overdose situations, it can lead to seizures and metabolic acidosis due to its metabolic byproducts. Pyridoxine works as an effective antidote because it can counteract the effects of isoniazid by replenishing pyridoxal phosphate, which is a cofactor in the synthesis of neurotransmitters. This action helps to mitigate the toxic effects of isoniazid, particularly in restoring normal brain function and reducing the risk of seizures.

In contrast, the other options, such as protamine, dimercaprol, and deferoxamine, are specific antidotes for different types of toxicities. Protamine is used to reverse heparin anticoagulation, dimercaprol is effective against heavy metal poisonings, and deferoxamine is utilized in cases of iron overload. Therefore, these substances would not be suitable for treating isoniazid toxicity. Understanding the specific antidote for different toxicities is critical for effective emergency treatment in clinical settings.