Thiamine (Vitamin B1)

• Essential vitamin in aerobic carbohydrate metabolism; deficiency impairs pyruvate dehydrogenase and other key enzymes → shunts metabolism toward lactate and energy failure in high-demand tissues (brain, heart)
• Core ED/ICU uses: treatment and prophylaxis of Wernicke encephalopathy, empiric supplementation in alcohol use disorder, severe malnutrition, and refeeding syndrome risk, and sometimes as an adjunct in septic shock with high lactate
• Thiamine is extremely safe, inexpensive, and often underused; many patients with alcohol use disorder or malnutrition have clinically significant deficiency
• Classic teaching: give thiamine before or with significant glucose loads in suspected deficiency to avoid worsening Wernicke encephalopathy (evidence imperfect, but high face validity and negligible downside)
• IV is preferred in acutely ill and malabsorptive patients; transition to oral thiamine once stable and able to absorb enterally

• Generic Name: Thiamine hydrochloride
• Brand Names: No single dominant brand; available as generic injection and tablets

Water-soluble vitamin (B1); cofactor in carbohydrate metabolism and neuronal function

Mechanism of Action:

• Converted in tissues to thiamine pyrophosphate (TPP), an essential cofactor for multiple enzymes in carbohydrate metabolism including pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase
• These enzymes link glycolysis to the Krebs cycle and the pentose phosphate pathway; deficiency impairs ATP production and increases lactate generation
• Brain and myocardium are especially vulnerable, leading to Wernicke encephalopathy (ocular abnormalities, ataxia, confusion) and beriberi (cardiomyopathy, neuropathy)
• Repletion restores oxidative metabolism, improves lactate clearance, and can reverse early neurologic findings if given promptly

Pharmacokinetics:

• Absorption: Oral absorption is efficient at low doses but saturable; in severe deficiency, malabsorption, or critical illness, IV dosing is preferred initially
• Distribution: Widely distributed, with high uptake in heart, liver, kidneys, and brain; body stores are limited and can be depleted within 2–3 weeks of inadequate intake
• Metabolism: Thiamine is phosphorylated intracellularly to active coenzyme forms (TPP); excess is metabolized to inactive forms
• Elimination: Water-soluble; excess excreted in urine. No significant accumulation even with high parenteral doses for short courses
• Because stores are limited but turnover is modest, regular replacement is needed in ongoing high-risk states (alcohol use disorder, malnutrition, chronic diuretic use)

• Suspected or confirmed Wernicke encephalopathy (ocular abnormalities, ataxia, confusion) in patients with alcohol use disorder, malnutrition, or hyperemesis (including pregnancy)
• Empiric prophylaxis in patients with alcohol use disorder, especially when hospitalized or NPO, or during acute illness
• Severe malnutrition and refeeding syndrome risk, particularly when starting calories or parenteral nutrition
• Adjunctive therapy in septic shock or unexplained lactic acidosis in patients with possible deficiency, recognizing evidence is mixed but risk is low
• Supportive treatment in heart failure due to beriberi (rare in high-income settings but important in global and resource-limited contexts)
• Diseases & Conditions: Wernicke encephalopathy and Wernicke–Korsakoff syndrome, alcohol-related malnutrition, refeeding syndrome, hyperemesis gravidarum with prolonged vomiting, unexplained high lactate/anaplerotic failure states

Available Forms:

• Injection: Typically 100 mg/mL in 1 mL vials or ampules for IV/IM use
• Oral tablets: Common strengths 50 mg and 100 mg
• Multivitamin preparations: Often contain small amounts of thiamine (e.g., 1–10 mg), which are inadequate to treat acute deficiency but helpful for maintenance
• Thiamine is often bundled in 'banana bags' or combination solutions, but high-dose replacement usually requires separate thiamine vials

Dosing – Thiamine (Adult ED/ICU):

Always follow local protocols and consult current drug references

• Known hypersensitivity to thiamine or formulation components (rare)

Common:

• Mild injection-site discomfort or irritation
• Transient flushing or pruritus (uncommon)

Serious (rare):

• Anaphylaxis or anaphylactoid reactions with IV administration (very rare)

• Clinical response in suspected Wernicke encephalopathy: improvement in ocular findings, gait/ataxia, and mental status over days
• Nutritional status, ongoing alcohol use, and risk of recurrent deficiency
• No routine serum thiamine level monitoring is required in most settings; deficiency is largely a clinical diagnosis in ED/ICU

• Occasional anaphylactoid reactions reported with rapid IV injection; minimize risk by infusing slowly (e.g., over 30 minutes) rather than IV push in high doses
• No specific renal or hepatic dose adjustments are generally required; toxicity is extremely low even at high parenteral doses

• Lexicomp. (2024). Thiamine: Drug information. Wolters Kluwer.
• Sechi, G., & Serra, A. (2007). Wernicke's encephalopathy: New clinical settings and recent advances in diagnosis and management. The Lancet Neurology, 6(5), 442–455.
• Farkas, J. (2022). Thiamine deficiency. EMCrit Project / IBCC. https://emcrit.org/