From the FDA Drug Label
Adverse Reactions ... Other neurotoxic effects, which are uncommon with conventional doses, are ... toxic psychosis. The relationship between Isoniazid (Isonicotinic Hydrazide) and psychosis is that toxic psychosis is an uncommon neurotoxic effect of the drug, especially with conventional doses.
- Psychosis is a potential adverse reaction associated with Isoniazid use.
- The exact mechanism and frequency of this reaction are not specified in the label, but it is mentioned as one of the neurotoxic effects of the drug 1.
From the Research
Isoniazid-induced psychosis is a rare but serious neuropsychiatric side effect of isoniazid, and if a patient develops psychotic symptoms while on isoniazid, the medication should be discontinued immediately and psychiatric evaluation sought. This adverse reaction occurs in approximately 1-2% of patients on isoniazid therapy, with higher risk in those with a history of mental illness, alcoholism, diabetes, malnutrition, or advanced age 2. The psychosis is believed to result from isoniazid's interference with pyridoxine (vitamin B6) metabolism, which affects neurotransmitter production in the brain.
Key Points
- Symptoms of isoniazid-induced psychosis typically include hallucinations, paranoid delusions, personality changes, and disorganized thinking 2.
- Preventive measures include routine supplementation with pyridoxine (25-50 mg daily) for all patients on isoniazid therapy 3.
- If psychosis develops, treatment involves discontinuation of isoniazid, administration of higher-dose pyridoxine (100-200 mg daily), and possibly antipsychotic medications for symptom management 4, 5.
- Most cases resolve within days to weeks after stopping isoniazid, though some patients may require longer psychiatric support 6.
- Alternative tuberculosis treatment regimens that exclude isoniazid should be considered for these patients.
Risk Factors
- History of mental illness
- Alcoholism
- Diabetes
- Malnutrition
- Advanced age
- Family and personal history of mental illness 4