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Vitamin B1 (Thiamine) — deficiency treatment / Wernicke's encephalopathy prevention Pregnancy: Safe and important in pregnancy (severe hyperemesis gravidarum — thiamine deficiency risk).

Thiamine (IV/IM — Pabrinex)

Brand names: Pabrinex IV High Potency

Adult dose

Dose: Wernicke's / high-risk alcohol use: 2 pairs of Pabrinex IV High Potency ampoules TDS for 3–5 days (each pair = 250 mg thiamine)
Route: IV (infusion in 100 mL NaCl over 30 min) or IM
Frequency: Three times daily (acute Wernicke's); once or twice daily (prophylaxis)
Max: 2 pairs TDS (acute); 1 pair OD (prophylaxis)
Wernicke's encephalopathy (confirmed or suspected): 2 pairs Pabrinex IV TDS for 3–5 days, then 1 pair OD for 2 weeks. Prophylaxis (alcohol withdrawal, malnourished patients): 1 pair Pabrinex IV/IM BD-TDS. Give BEFORE glucose (glucose precipitates Wernicke's in thiamine-deficient patients).

Paediatric dose

Route: IV
Frequency: Specialist guidance
Max: Specialist guidance
Paediatric thiamine deficiency: specialist guidance. Thiamine 50–100 mg IV/IM OD (general) or BNFc guidance.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required (treatment for alcohol-related hepatic disease).

Clinical pearls

  • Give BEFORE IV glucose in alcohol-related emergency (thiamine needed to metabolise glucose — glucose first precipitates encephalopathy)
  • Diagnosis of Wernicke's: triad — confusion, ataxia, ophthalmoplegia (only 10–20% have all three)
  • Oral thiamine inadequate for treatment (absorption impaired in alcohol dependency) — IV/IM essential
  • Pabrinex contains Vitamins B1, B2, B3, B6, C — broad vitamin B replacement
  • Cheap, widely available, lifesaving — should be given liberally in malnourished/alcohol-use patients

Contraindications

  • Hypersensitivity to thiamine or Pabrinex components (anaphylaxis risk — rare)

Side effects

  • Anaphylaxis (rare — have resuscitation equipment available)
  • Local irritation at injection site
  • Flushing

Interactions

  • No significant drug interactions

Monitoring

  • Clinical response (confusion, eye movements, gait)
  • Glucose levels

Reference: BNFc; BNF; NICE CG100 Alcohol Dependence; RCP Acute Care Handbook. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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