II. Pharmacokinetics

  1. Absorption rapid
  2. Peak levels: 1 to 2 hours
  3. Toxic Levels: >20 mg/kg

III. Mechanism: Toxicity

  1. Pyridoxine Deficiency
  2. Glutamic Dehydrogenase inhibition
    1. Blocks conversion of glutamate to GABA
    2. Results in GABA deficiency

V. Labs

  1. See Unknown Ingestion for broad based lab evaluation after ingestion
  2. Labs in isolated Isoniazid ingestion
    1. Bedside Glucose
    2. Basic metabolic profile
    3. Creatinine Phosphokinase

VI. Imaging

VII. Diagnostics

  1. Electroencephalogram (EEG) monitoring
    1. Indicated in persistant or recurrent Seizures

VIII. Management

  1. Decontamination
    1. Activated Charcoal 1 g/kg if presenting within one hour of ingestion, and airway protected
    2. Consider Hemodialysis if started early in large ingestions
  2. Pyridoxine
    1. Give same dose of Pyridoxine of the Isoniazid ingestion if known OR
    2. Pyridoxine 70 mg/kg (up to 5 g) IV over 3 to 5 minutes
    3. May repeat dosing for recurrent Seizures
  3. Seizures
    1. See Status Epilepticus
    2. Lorazepam 0.5 to 1 mg/kg (up to 2 mg/dose) as needed
  4. Disposition
    1. Observe or admit all patients with recurrent Seizures or persistent Altered Mental Status
    2. May discharge after 4 to 6 hours following ingestion if asymptomatic

IX. References

  1. Tomaszewski (2018) Crit Dec Emerg Med 32(7):28

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