Thiamine

Thiamine

• Thiamine is vitamin B1. Thiamine is found in foods such as cereals, whole grains, meat, nuts, beans, and peas. Thiamine is important in the breakdown of carbohydrates from foods into products needed by the body. Thiamine is used to treat or prevent vitamin B1 deficiency.

• Thiamine injection is used to treat beriberi, a serious condition caused by prolonged lack of vitamin B1. Thiamine taken by mouth (oral) is available without a prescription. Injectable thiamine must be given by a health-care professional.

Mechanism of Action:

• Thiamine combines with adenosine triphosphate (ATP) in the liver, kidneys, and leukocytes to produce thiamine diphosphate. Thiamine diphosphate acts as a coenzyme in carbohydrate metabolism, in transketolation reactions, and in the utilization of hexose in the hexose-monophosphate shunt.

• Dosage: Usual adult dose for thiamine deficiency: If dextrose administered: to patients with marginal thianine status, give 100 mg in each of the first few liters of IV fluid to avoid precipitating heart failure. Usual adult dose for vitamin/mineral supplementation: For beriberi, 10-20 mg IM three times daily for up to 2 weeks.

• Thereafter, use an oral therapeutic multivitamin preparation containing 5-10 mg thiamine daily for 1 month. 50-100 mg orally once a day usual adult dose for Wernicke's Encephalopathy: 100 mg IV as an initial dose followed by 50-100 mg/day IM or IV until the patient is on a regular, balanced diet. Usual pediatric dose for beriberi: 10-25 mg.

• IM or IV daily (if critically ill), or 10-50 mg orally every day for 2 weeks, then 5-10 mg orally daily for I month. If collapse occurs: 25 mg IV. Administer with caution. Usual pediatric dose for thiamine deficiency: If dextrose administered to patients with marginal thiamine status, give 100 mg in each of the first few liters of IV fluid to avoid precipitating heart failure. Usual pediatric dose for vitamin/mineral supplementation: Infant: 0.3-0.5 mg orally once a day; children: 0.5-1 mg orally once a day.

Precautions:

• Thiamine supplementation is reported to be well-tolerated and safe to use. A retrospective study on adverse effects of thiamine supplementation among more than 300,000 patients found no serious side effects. However, some commonly reported adverse effects include nausea, urticaria, lethargy, ataxia, and impaired gut motility.

Interactions:

• Laboratory studies suggest that digoxin, a medication used to treat heart conditions, may reduce the ability of heart cells to absorb and use vitamin B1.

• This may be particularly true when digoxin is combined with furosemide (Lasix, a loop diuretic). Diuretics, particularly furosemide (Lasix), which belongs to a class called loop diuretics, may reduce levels of vitamin B1 in the body. It is possible that other diuretics may have the same effect. Preliminary evidence suggests that some people taking phenytoin have lower levels of thiamine in their blood, which may contribute to the side effects of the drug. However, this is not true of all people who take phenytoin.