Pyridoxine / Vitamin B6

Liverpool Hospital Emergency Department


  • Isoniazid overdose 
  • Ethylene Glycol overdose (cofactor in glyoxylic acid metabolism) 


  • IV 50mg/ml
  • PO 25mg /50mg/ 100mg 

Dosage and Administration 

  • Isoniazid Overdose
  • Intravenous:
    • Dosage is equivalent to amount of Isoniazid ingested 1:1 ratio (e.g.  4g isoniazid requires 4g of pyridoxine)
    • Maximum dose is 5g via infusion at a rate of 500mg/minute.
    • Seizures, acidosis or unknown dose and very unwell should be  managed with pyridoxine – 5g IV
  • Oral: 
    • Dosage is equivalent to the amount of Isoniazid ingested 1:1 ratio
    • Charcoal will reduce bioavailability of oral pyridoxine
  • Ethylene glycol overdose:
    • 50mg IV 6 hourly for 2 days (thiamine is an alternative) 

Side Effects: 

  • Chronic high doses can cause peripheral neuropathy
  • Hypersensitivity can occur 

Pit Falls: 

  • Low dose available therefore po may be a more viable alternative
  • If insufficient IV dosing available and seizures are present consider benzodiazepines  and barbiturates. (Other anticonvulsants are not effective)