Thiamine is administered orally and by intramuscular or intravenous injection. Thiamine is widely distributed. Body storage of thiamine is limited to about 30 mg. Thiamine is distributed into breast milk at a rate of about 100—200 mcg daily from normal dietary intake. There is little excretion of thiamine or its metabolites at physiologic doses. Following large doses, saturation occurs, with subsequent renal excretion as pyrimidine.
Oral Route: Small oral doses are readily absorbed from the GI tract, but absorption of large doses is limited. Administration with food reduces the rate of absorption.
Intramuscular Route: Following IM administration of thiamine, vitamin B1, absorption is rapid and complete.
Hepatic Impairment: Patients with cirrhosis have a decreased extent of absorption of thiamine, vitamin B1.
Alcoholism: Alcoholics have a decreased extent of absorption of thiamine, vitamin B1.
Malabsorption: Patients with malabsorption have a decreased extent of absorption of thiamine, vitamin B1.