Thiamine Dosing in Alcohol Withdrawal
All patients with alcohol withdrawal syndrome should receive thiamine 100-300 mg/day for prevention of Wernicke's encephalopathy, with higher doses of 100-500 mg/day required if Wernicke's encephalopathy is already established. 1
Dosing Algorithm Based on Clinical Presentation
For Prevention of Wernicke's Encephalopathy (Standard Alcohol Withdrawal)
- Administer 100-300 mg/day thiamine for 4-12 weeks 1, 2
- The parenteral route (IV or IM) is strongly preferred initially due to poor gastrointestinal absorption in alcoholic patients 2
- Continue for 2-3 months following resolution of withdrawal symptoms 1
For Established Wernicke's Encephalopathy
- Administer 100-500 mg/day thiamine for 12-24 weeks 1, 2
- The FDA label recommends an initial IV dose of 100 mg, followed by IM doses of 50-100 mg daily until regular diet is resumed 3
- Recent evidence supports even higher doses (500 mg) when symptoms persist on lower doses, with rapid resolution of altered mental status and ophthalmoplegia 4
For High-Risk Patients Receiving IV Dextrose
- Give 100 mg thiamine in each of the first few liters of IV fluid to prevent precipitating acute heart failure 3
- This is critical because IV glucose can precipitate acute thiamine deficiency 1, 2
Route of Administration
Thiamine must be given BEFORE any glucose-containing fluids to prevent precipitating acute Wernicke's encephalopathy 1, 2
- Parenteral (IV or IM) route is preferred initially over oral administration due to unreliable gastrointestinal absorption in alcoholic patients 2
- Transition to oral thiamine (250-300 mg/day) after acute phase for maintenance 5
Safety Considerations
The risk of anaphylactic shock from parenteral thiamine is extremely low (less than 1 in 100,000), making the benefits far outweigh the risks 6
- In "wet" beriberi with myocardial failure, thiamine must be administered slowly by IV route 3
- All patients experienced symptom improvement across a wide range of doses (100-1500 mg) with minimal adverse events 7
- High-dose IV thiamine (≥500 mg) is reliable and low-risk even at these elevated doses 4
Common Pitfalls to Avoid
- Never administer glucose-containing IV fluids before thiamine replacement - this can precipitate acute Wernicke's encephalopathy 1, 2, 3
- Do not rely on oral thiamine alone in acute withdrawal - absorption is compromised in alcoholic patients 2
- Do not underdose - doses of at least 100 mg are required, and higher doses (200-500 mg three times daily) are recommended for established Wernicke's encephalopathy 5
- Do not delay treatment - Wernicke's encephalopathy has 20% acute mortality and is frequently underdiagnosed and undertreated 5, 6