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Introduction

  1. Pharmacology. Thiamine (vitamin B1) is a water-soluble vitamin that acts as an essential cofactor for various carbohydrate metabolic pathways. Thiamine deficiency may be seen with chronic excessive alcohol use, malnutrition, malabsorption, persistent vomiting, and hypermetabolic states. Patients can present with complications such as beriberi or Wernicke-Korsakoff syndrome. Thiamine is rapidly absorbed by oral, intramuscular, or intravenous administration. Magnesium is required for optimal thiamine function.
  2. Indications
    1. Empiric therapy to prevent and treat Wernicke-Korsakoff syndrome, beriberi, malnourished patients, or any patient presenting with an altered mental status of unknown etiology. Thiamine should be given concurrently with glucose in such cases.
    2. Adjunctive treatment in ethylene glycol ingestions to possibly enhance detoxification of glyoxylic acid.
    3. Potential role in treatment of refractory lactic acidosis and sepsis.
  3. Contraindications. Use caution in patients with known sensitivity to thiamine or preservatives. Some thiamine preparations contain aluminum and should be used with caution in patients with renal impairment.
  4. Adverse effects
    1. Anaphylactoid reactions, vasodilation, hypotension, pruritus, weakness, cyanosis, and angioedema after rapid intravenous injection. Reactions are rare with newer preparations.
    2. Acute pulmonary edema in beriberi patients due to a rapid increase in vascular resistance.
    3. Use in pregnancy. FDA Category A for doses up to the recommended daily allowance (RDA) and Category C for doses above the RDA (Introduction).
  5. Drug or laboratory interactions. Furosemide is reported to increase urinary thiamine excretion. Fluorouracil may increase thiamine metabolism and block formation of its active form.
  6. Dosage and method of administration.
    1. Thiamine deficiency: give 100 mg IV slowly over 5 minutes or by IM injection, followed by 100 mg TID for 1-2 days and re-evaluate clinically. For Wernicke encephalopathy, give 500 mg TID for 2-3 days, then 200-300 mg daily for 5 days. Consider co-administration of magnesium sulfate (2 g IV in patients with intact renal function), especially if they appear to be refractory to treatment.
    2. Ethylene glycol toxicity: 100 mg IV daily until intoxication resolves.