PDP-Isoniazid Overdosage

Symptoms: Manifestations of isoniazid overdosage are apparent within 30 minutes to 3 hours. Nausea, vomiting, dizziness, slurring of speech, blurring of vision and visual hallucinations (including bright colors and strange designs), are among the early manifestations. With marked overdosage, respiratory distress and CNS depression, progressing rapidly from stupor to profound coma, are to be expected, along with severe, intractable seizures. Severe metabolic acidosis, acetonuria and hyperglycemia are typical laboratory findings.
Treatment: Treatment of overdosage consists of careful emesis and lavage usually following intubation, correction of any acidosis with sodium bicarbonate, administration of IV anticonvulsants and the IV injection of large doses of pyridoxine (e.g., a gram-for-gram dose equivalent to the amount of isoniazid ingested). See Vitamin B6 General Monograph. Forced diuresis may be tried and hemodialysis or peritoneal dialysis has been used.
For management of a suspected drug overdose, contact the regional Poison Control Centre immediately.