Coma from long-term overingestion of isoniazid

Area of Science:

• Neuroscience
• Clinical Toxicology
• Pharmacology

Background:

• Isoniazid is a primary treatment for tuberculosis.
• Overingestion of isoniazid can lead to severe central nervous system (CNS) toxicity, including confusion, seizures, and coma.
• Most CNS toxic reactions result from acute overdose, but chronic toxicity is also possible.

Observation:

• A patient on 1200 mg daily isoniazid for 6 weeks presented with confusion and lethargy, progressing to coma.
• The patient's symptoms were initially attributed to potential neurosyphilis, delaying the diagnosis of isoniazid toxicity.
• The patient had no history of sudden overdose.

Findings:

• Intravenous administration of 1 g pyridoxine hydrochloride (vitamin B6) resulted in rapid and complete reversal of CNS symptoms.
• The patient became fully alert and lucid within 30 minutes of pyridoxine treatment.
• This case highlights that chronic isoniazid use, even without acute overdose, can precipitate severe CNS toxicity.

Implications:

• Pyridoxine hydrochloride is a crucial and effective antidote for isoniazid-induced neurotoxicity.
• Clinicians should maintain a high index of suspicion for isoniazid poisoning in patients presenting with unexplained neurological symptoms, regardless of overdose history.
• Early recognition and treatment with pyridoxine can prevent severe outcomes and facilitate recovery.