Dosing and uses of Vitamin B1 (thiamine)
Adult dosage forms and strengths
tablet
- 50mg
- 100mg
- 250mg
capsule
- 50mg
injectable solution
- 100mg/mL
RDa
Males: 1.2 mg/day
Females: 1.1 mg/day
Pregnancy/Lactation: 1.4 mg/day
Beriberi
IM: 5-30 mg three times daily (if critically ill); then 5-30 mg three times daily for 1 month
Duration dependent on persistence of symptoms
Wernicke Encephalopathy
100 mg IV; then 50-100 mg/day IM or IV until consuming regular balanced diet
Thiamin Deficiency
1 tablet or capsule/day
Need for thiamin increases when carbohydrate content of diet is high
Pediatric dosage forms and strengths
tablet
- 50mg
- 100mg
- 250mg
capsule
- 50mg
injectable solution
- 100mg/mL
RDa
0-6 months: 0.2 mg/day
6-12 months: 0.3 mg/day
1-3 years old: 0.5 mg/day
3-8 years old: 0.6 mg/day
8-13 years old: 0.9 mg/day
13-18 years old: 1.2 mg/day (male), 1 mg/day (female)
Deficiency
10-50 mg/day PO in divided doses
Beriberi
10-25 mg IV/IM qDay (if crtically ill) or 10-50 mg/dose PO qDay for at least 2 weeks, THEn
5-10 mg/day PO for 1 month
Duration dependent on persistence of symptoms
Vitamin B1 (thiamine) adverse (side) effects
Frequency not defined
Warmth
Anaphylaxis
Cyanosis
Diaphoresis
Restlessness
Angioneurotic edema
Pruritus
Urticaria
Pulmonary edema
Weakness
Tightness of the throat
Nausea
Warnings
Contraindications
Hypersensitivity
Cautions
In pregnancy (doses >RDA)
Acute thiamine deficiency reported with dextrose administration; use caution when thiamine status uncertain
Hypersensitivity reactions reported following repeated parenteral doses
Parenteral products may contain aluminum; use caution in patients with impaired renal function
Evaluate for additional vitamin deficiencies if patient diagnosed with thiamin deficiency; single vitamin deficiencies are rare
Pregnancy and lactation
Pregnancy category: A (injectable); C (if >RDA)
Lactation: Safe
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Nutrition
Sources: brewer's yeast, pork, ham, liver, whole grains, peas, beans, milk
Function: cofactor in glucose metabolism
Deficiency: (common in alcoholics, Asians, dialysis patients, those on high carbohydrate diet) Beriberi; causes nerve damage, dementia, heart failure; sometimes irreversible
Reduced/Destroyed by
Heat-labile thiaminases contained in milled rice, raw shellfish & freshwater fishes
Heat-stable anti-thiamine factor in coffee/tea
Sulfite-containing foods
AlcohoL
High temp
Toxicity Symptoms
Toxicity: rare; intake of >400 mg/d; lethargy, balance problems, intestinal problems
Pharmacology of Vitamin B1 (thiamine)
Mechanism of action
Forms thiamine pyrophosphate by combining with adenosine triphosphate; essential coenzyme in carbohydrate metabolism
Pharmacokinetics
Distribution: Distributes mainly to heart, brain, kidney, and liver
Excretion: Urine
Absorption: Adequate (PO); rapid and complete (IM)
Administration
When oral administration is not feasible
When malabsorption is suspected
In patients with Wernicke's encephalopathy or high-output heart failure secondary to beriberi
IV administration preferred for high-output heart failure
Compatible with most common diluents (dextrose solutions; LR, Ringer's; dextrose-saline solutions; dextrose/LR; NS; ½NS; fat emulsion 10%; Na-lactate 1M/6
