What are the effects of high-dose thiamine (Vitamin B1)?

From the Guidelines

High-dose thiamine therapy, involving doses of 100-300 mg per day, is recommended for patients at risk of thiamine deficiency, including those with prolonged vomiting, dysphagia, or high alcohol consumption, as well as those undergoing bariatric surgery. This recommendation is based on the most recent and highest quality study, which suggests that thiamine can be administered orally, enterally, or intravenously, with the intravenous route being the most efficient in acute deficiency symptoms 1. The study also recommends that patients with suspected thiamine deficiency should be treated immediately, without waiting for test results, to prevent the development of Wernicke's encephalopathy 1.

Key Points

• High-dose thiamine therapy is used to treat severe thiamine deficiency conditions, such as Wernicke-Korsakoff syndrome, and to prevent thiamine deficiency in patients at risk.
• The recommended dose of thiamine is 100-300 mg per day, which can be administered orally, enterally, or intravenously.
• Intravenous administration is the most efficient route in acute deficiency symptoms, but should be done slowly to avoid rare anaphylactic reactions.
• Patients should be monitored for potential side effects, such as nausea, sweating, or restlessness, although these are uncommon.

Clinical Considerations

• Patients undergoing bariatric surgery are at high risk of developing thiamine deficiency, and should be educated about the potential risks and importance of seeking early advice if symptoms occur.
• Clinicians should be aware of the factors that may predispose to thiamine deficiency, and initiate immediate treatment if suspected.
• Thiamine deficiency can have severe consequences if left untreated or treated late, making early recognition and treatment crucial.

From the FDA Drug Label

OVERDOSAGE: Parenteral doses of 100 to 500 mg singly have been administered without toxic effects. However, dosages exceeding 30 mg three times a day are not utilized effectively. When the body tissues are saturated with thiamine, it is excreted in the urine as pyrimidine. As the intake of thiamine is further increased, it appears unchanged in the urine. The effects of high-dose thiamine are:

• No toxic effects were observed with parenteral doses of 100 to 500 mg
• Doses exceeding 30 mg three times a day are not utilized effectively
• High intake of thiamine is excreted in the urine, either as pyrimidine or unchanged 2

From the Research

Effects of High-Dose Thiamine

The effects of high-dose thiamine have been studied in various contexts, including the treatment of Wernicke's encephalopathy, Wernicke-Korsakoff syndrome, and biotin-thiamine-responsive basal ganglia disease.

• High-dose thiamine appears to be safe and efficacious for use in patients with suspected Wernicke's encephalopathy, with 73% of patients displaying symptom resolution or improvement after treatment 3.
• However, a randomized controlled trial found no significant differences in cognitive function or neurological functioning between patients receiving high-dose thiamine and those receiving lower doses for the treatment and prevention of Wernicke-Korsakoff syndrome 4.
• A retrospective study found no statistically significant difference in the time to resolution of Wernicke's encephalopathy symptoms for patients receiving high-dose versus low-dose thiamine 5.
• High-dose thiamine has been shown to be effective in treating patients with biotin-thiamine-responsive basal ganglia disease, with significant improvement in symptoms after increasing the thiamine dose to 75 mg/kg/day 6.
• High-dose thiamine therapy has also been found to produce a regression of urinary albumin excretion in type 2 diabetic patients with microalbuminuria, suggesting a potential role in the treatment of early-stage diabetic nephropathy 7.

Key Findings

• High-dose thiamine is safe and efficacious for treating Wernicke's encephalopathy 3.
• No clear benefit of high-dose thiamine over lower doses for Wernicke-Korsakoff syndrome 4.
• High-dose thiamine is effective in treating biotin-thiamine-responsive basal ganglia disease 6.
• High-dose thiamine therapy may be beneficial for type 2 diabetic patients with microalbuminuria 7.

Dosage and Administration

• High-dose thiamine has been defined as ≥500 mg intravenous thiamine 3 or ≥100 mg IV daily 5.
• Dosage regimens have varied across studies, with some using 100 mg thrice daily, 300 mg thrice daily, or 500 mg thrice daily 4.
• The optimal dosing strategy and duration of high-dose thiamine treatment are unclear and require further study 3, 4, 5.