Pharmacokinetics
 Oral vitamin B12 in the stomach and gastric parietal cells secrete intrinsic factor form of vitamin B12-intrinsic factor complex. When entering the complex back to the terminal ileum with the intestinal microvilli on the cell receptors, by endocytosis into intestinal cells, and then absorbed into the bloodstream. 8 to 12 hours after oral administration the plasma concentration reached its peak; intramuscular injection of 40 minutes, about 50% absorbed into the bloodstream.

  Intramuscular injection of vitamin B121mg, the plasma concentration over time in the 1ng/ml average 2.1 months. Vitamin B12 absorbed into the bloodstream and after transfer cobalamin combined into the organization.

 There are three transfer cobalamin, which turn vitamin B12 cobalamin Ⅱ is the main form of transport, accounting for the total plasma vitamin B12 levels in 2 / 3. The liver is the main storage site of vitamin B12. Total body storage of vitamin B12 is 3 ~ 5mg, of which 1 ~ 3mg stored in the liver. Oral vitamin B12, 24 hours after the concentration of vitamin B12 in the liver reached a peak. 5 to 6 days later, about 60 ~ 70% of the amount is still concentrated in the liver. Mainly excreted by the kidneys, in addition to the demand for foreign body, a few calls begin prototype with the urine.

 Intramuscular injection of vitamin B121mg, 72 hours later, 75% of the total prototype with the urine. Urinary excretion increased with the amount injected, after intramuscular injection of 5μg 8 hours discharge 3 ~ 4μg; intramuscular injection of 1mg after eight hours excretion of up to 330 ~ 470μg.