Generic Name: Thiamine
Alternative Names: Vitamin B1, aneurin
Drug Class: Water-soluble B-vitamin (part of the B-complex group)
Chemical Class: Pyrimidine-substituted thiazole derivative
Dosage Forms: Oral tablets, capsules, and liquids (10 mg to 100 mg); injectable solution (intramuscular or intravenous; typically 100 mg/mL)
Molecular Formula: C12H17N4OS+
Physiological Form: Thiamine pyrophosphate (TPP) is the biologically active coenzyme
Thiamine is an essential water-soluble micronutrient that serves as a critical cofactor for enzymatic processes involved in carbohydrate metabolism, nervous system function, and muscle coordination. It must be obtained from diet or supplementation, as the human body cannot synthesize it. It is rapidly taken up and utilized by cells, especially those with high energy demand such as neurons, hepatocytes, and cardiac myocytes.
2. Physiological Role
Thiamine is primarily involved in oxidative energy metabolism, neurotransmission, and cellular signaling. It functions as a coenzyme in several key biochemical pathways:
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Pyruvate dehydrogenase complex (converts pyruvate to acetyl-CoA)
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Alpha-ketoglutarate dehydrogenase (Krebs cycle enzyme)
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Branched-chain ketoacid dehydrogenase (amino acid catabolism)
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Transketolase (pentose phosphate pathway)
Thiamine plays a vital role in maintaining neural conductivity, myelin sheath integrity, and efficient glucose utilization in the brain. It supports cardiovascular function by facilitating myocardial energy production.
3. Dietary Requirements
Recommended Daily Intake (RDI):
| Age Group | Male | Female |
|---|---|---|
| Infants (0–6 months) | 0.2 mg/day | 0.2 mg/day |
| Children (1–3 years) | 0.5 mg/day | 0.5 mg/day |
| Children (4–8 years) | 0.6 mg/day | 0.6 mg/day |
| Adolescents (9–13 years) | 0.9 mg/day | 0.9 mg/day |
| Teens (14–18 years) | 1.2 mg/day | 1.0 mg/day |
| Adults (≥19 years) | 1.2 mg/day | 1.1 mg/day |
| Pregnancy | — | 1.4 mg/day |
| Lactation | — | 1.5 mg/day |
4. Sources of Thiamine
Rich Dietary Sources:
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Whole grains (brown rice, oats, barley)
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Fortified cereals and bread
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Legumes (lentils, beans, peas)
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Pork and organ meats (especially liver)
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Nuts and seeds (sunflower, sesame)
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Eggs and dairy in smaller amounts
Thiamine is heat-sensitive and water-soluble; boiling and prolonged cooking may reduce its content in food. Processing (refining of grains) significantly lowers thiamine levels.
5. Pharmacokinetics
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Absorption: Absorbed in the jejunum and ileum via active transport (low doses) and passive diffusion (high doses)
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Distribution: Distributed in plasma and intracellular compartments, especially muscle, liver, kidney, heart, and brain
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Activation: Converted in the liver and tissues to thiamine pyrophosphate (TPP)
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Half-Life: Plasma half-life is 1 to 12 hours; tissue half-life is 9 to 18 days
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Excretion: Primarily renal excretion; urinary output increases with high intake or impaired absorption
6. Clinical Indications
6.1 Thiamine Deficiency (Hypovitaminosis B1)
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Beriberi (wet or dry):
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Wet form: cardiovascular symptoms including tachycardia, heart failure, edema
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Dry form: peripheral neuropathy, muscle wasting, ataxia
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Wernicke’s Encephalopathy:
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Acute neurological emergency caused by severe deficiency
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Classic triad: confusion, ataxia, ophthalmoplegia
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Seen in chronic alcohol use, malnutrition, eating disorders, hyperemesis gravidarum
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Korsakoff’s Syndrome:
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Chronic neuropsychiatric sequel of untreated Wernicke’s
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Symptoms include anterograde and retrograde amnesia, confabulation, disorientation
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Other conditions:
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Peripheral neuropathy
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Congestive heart failure due to deficiency-related myocardial energy deficit
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Dialysis-associated deficiency
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Refeeding syndrome
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7. Therapeutic Uses
7.1 Replacement Therapy
Oral:
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Mild deficiency: 10–100 mg once daily
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Prevention in at-risk patients (e.g., bariatric surgery): 50–100 mg daily
Parenteral (IM or IV):
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Wernicke’s encephalopathy: 100–500 mg IV every 8 hours for 2–3 days
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Beriberi: 100–200 mg IM or IV daily until resolution, then switch to oral
7.2 Prophylaxis
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Alcohol-dependent individuals: 50–100 mg oral daily
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Patients on chronic diuretics, dialysis, or total parenteral nutrition
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Hyperemesis gravidarum patients receiving glucose without B-vitamin co-administration
7.3 Adjunct Uses
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Supportive treatment in diabetic neuropathy
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Prevention of lactic acidosis in pyruvate dehydrogenase complex disorders
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Experimental use in sepsis or critical illness (with vitamin C and hydrocortisone)
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High-dose thiamine trials for Alzheimer’s disease and cognitive dysfunction
8. Dosage and Administration
8.1 Oral Dosage
| Use Case | Typical Dose |
|---|---|
| Mild deficiency | 25–100 mg once daily |
| Maintenance / prophylaxis | 10–50 mg daily |
| Alcohol misuse | 100 mg once or twice daily |
| Refeeding or TPN | 100–300 mg/day |
8.2 Parenteral Dosage
| Condition | Dose |
|---|---|
| Wernicke’s encephalopathy | 100–500 mg IV every 8–12 hours |
| Severe deficiency | 100–200 mg IM or IV daily |
| Prophylaxis (IM) | 100 mg daily for 3–5 days |
9. Safety and Toxicity
Thiamine is generally non-toxic due to its water solubility and rapid renal excretion. Even high oral doses are well tolerated.
9.1 Adverse Effects (Rare)
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Local irritation at injection site
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Hypersensitivity reactions (rare with IV use): rash, hypotension, pruritus
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Anaphylaxis (extremely rare, usually with rapid IV push)
10. Drug Interactions
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Furosemide: increases urinary excretion of thiamine, leading to potential depletion
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5-Fluorouracil: inhibits thiamine phosphorylation, possibly inducing deficiency
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Alcohol: reduces intestinal absorption and hepatic phosphorylation
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Oral contraceptives: may interfere with thiamine metabolism in high-dose users
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Loop diuretics: increase renal clearance
11. Risk Factors for Deficiency
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Chronic alcoholism
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Hyperemesis gravidarum
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Anorexia nervosa
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Bariatric surgery
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Total parenteral nutrition (without supplementation)
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High-carbohydrate intravenous feeding (glucose infusions)
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Prolonged diarrhea or vomiting
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Malabsorption syndromes (e.g., celiac disease, IBD)
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Dialysis (peritoneal or hemodialysis)
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Certain cancers or advanced HIV/AIDS
12. Monitoring Parameters
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Clinical symptom resolution (e.g., improvement in mental status, neuropathy, cardiovascular signs)
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Blood thiamine concentration or thiamine diphosphate (TPP) level
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Erythrocyte transketolase activity (functional marker)
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Urinary thiamine excretion in 24-hour collections
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Regular neurologic and cognitive assessments in at-risk populations
13. Storage and Handling
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Oral forms: store at 15–30 °C, protect from moisture
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Injectable: store in original amber vial at room temperature, protect from light
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Avoid freezing injectable preparations
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Use immediately after opening vials to prevent contamination
14. Pediatric Considerations
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Deficiency may develop rapidly due to low body reserves
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Infantile beriberi manifests within 2–3 months with tachycardia, restlessness, vomiting, and sudden death
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Treatment involves IM/IV thiamine: 10–25 mg/day in infants
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Preventive supplementation recommended in exclusively breastfed infants of deficient mothers
15. Geriatric Use
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Elderly patients are at increased risk due to inadequate dietary intake, malabsorption, polypharmacy, and chronic illnesses
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Routine supplementation (10–50 mg daily) may prevent deficiency
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Caution advised in administering parenteral thiamine in patients with cardiac instability
16. Pregnancy and Lactation
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Requirements increase during pregnancy and lactation
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Oral thiamine is safe and well-tolerated; no teratogenicity observed
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High-dose parenteral therapy may be used in pregnant women with Wernicke’s or severe deficiency
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Breast milk concentration correlates with maternal intake; supplementation ensures adequate neonatal levels
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