Thiamin Hydrochloride

Trade Names:Thiamine Hydrochloride- Tablets 50 mg- Tablets 100 mg- Tablets 250 mg- Tablets 500 mg- Injection 100 mg/mL

Pharmacology

Thiamin, after conversion to thiamin pyrophosphate, functions with adenosine triphosphate (ATP) in carbohydrate metabolism. Deficiencies result in beriberi, characterized by GI manifestations, peripheral neuropathy, and cerebral deficits.

Pharmacokinetics

Absorption

Thiamin is a water-soluble vitamin. It is absorbed by both diffusion and active transport mechanisms. Absorption following IM administration is rapid and complete.

Distribution

Thiamin is widely distributed in all tissues, with highest concentrations in liver, brain, kidney, and heart. When thiamin intake exceeds needs, tissue stores increase more than 2 to 3 times. If intake is insufficient, tissues become depleted of their vitamin content.

Metabolism

Thiamin undergoes rapid metabolism. Thiamine + ATP → thiamine pyrophosphate (cocarboxylase) coenzyme.

Elimination

Excess thiamin is excreted in urine. Depletion of vitamin B ₁ occurs about 3 wk with absence of thiamin in diet.

Indications and Usage

Prophylaxis or treatment of thiamin deficiency (beriberi). Parenteral use indicated when oral therapy not feasible or advisable.

Unlabeled Uses

Mosquito repellant; treatment of ulcerative colitis, chronic diarrhea, cerebellar syndrome, polyneuritis; appetite stimulant; prevention of Wernicke-Korsakoff syndrome.

Contraindications

Standard considerations.

Dosage and Administration

PO 0.5 mg per 1,000 kcal intake. RDA is 1.2 to 1.5 mg (adult men), 1 to 1.1 mg (adult women).

0.8 to 1 mg.

0.3 to 0.5 mg (infants).

IV 10 to 30 mg 3 times daily. Treat as emergency cardiac condition.

IM 10 to 20 mg 3 times daily for 2 wk, then PO 5 to 10 mg (as part of multivitamin) for 1 mo.

IV 10 mg initially followed by IM 10 mg twice daily for 3 days, then 10 mg daily for 6 wk.

IV 50 to 100 mg; then IM/IV 50 to 100 mg/day until consuming normal diet; then PO 40 mg/day.

PO 10 to 20 mg daily; max doses of 4 g daily have been used.

Storage/Stability

Store in light-resistant container.

Drug Interactions

Unstable in neutral or alkaline solutions. Incompatible with sulfite containing solutions. Incompatible with barbiturates, erythromycin, lactobionate, citrates.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

CV collapse; hypotension; death.

CNS

Weakness; restlessness.

Dermatologic

Pruritus; urticaria.

EENT

Tightness of throat.

GI

Nausea; hemorrhage into GI tract.

Respiratory

Pulmonary edema; cyanosis.

Miscellaneous

Feeling of warmth; sweating; anaphylaxis; angioneurotic edema; local tenderness and induration (after IM use).

Precautions

Pregnancy

Category A ; ( Category C if used in doses greater than the RDA.)

Lactation

Undetermined.

Hypersensitivity

Can occur. Deaths have resulted from IV administration. Intradermal test dose is recommended if sensitivity is suspected.

Deficiency

Single vitamin B ₁ deficiency is rare; suspect multiple vitamin deficiencies.

Wernicke encephalopathy

May occur or worsen suddenly in thiamin-deficient patients given glucose. If deficiency is suspected, give thiamin before or with dextrose-containing fluids.

Patient Information

• Alert patient to potential lab test abnormalities.
• Inform patient of all potential adverse reactions and of importance of reporting problems to health care provider.
• Teach patient about proper nutritional balance needed in diet. Thiamin-rich foods are yeast, beef, liver, legumes, beans, and whole grains.

Copyright © 2009 Wolters Kluwer Health.