Pharmacotherapeutic group: antianemics, vitamin B12 (cyanocobalamin and analogues)
ATC code: B03BA01
As a member of the prosthetic groups of methylmalonyl-CoA isomerase, vitamin B12 is required for the conversion of propionic acid to succinic acid. In addition, vitamin B12, together with folic acid, participates in the formation of labile methyl groups, which are transferred by transmethylation to other methyl group-accepting molecules. This vitamin also influences the synthesis of nucleic acids, particularly during
hematopoiesis and other cell maturation processes.
Bioavailability and requirements
The human body is unable to synthesize vitamin B12 and obtains it by absorption from food. Foods containing vitamin B12 include liver, kidneys, heart, fish, oysters, milk, egg yolk, and meat. Vitamin B12 is administered for therapeutic purposes in the form of cyanocobalamin and/or hydroxocobalamin. Both substances are prodrugs that are converted in the body into the active forms methylcobalamin and
5-adenosylcobalamin. The daily requirement for vitamin B12 is approximately 1 µg.
Vitamin B12 deficiency may occur due to malabsorption, particularly in elderly patients (due to malabsorption of cobalamin from food), in patients following partial gastrectomy or ileostomy, or in other gastrointestinal tract disorders, as well as in cases of strict vegetarian diets.
Symptoms of deficiency
In many individuals, vitamin B12 deficiency is not accompanied by clinical symptoms, or symptoms are so mild that the deficit is not recognizable without biochemical blood testing (subclinical cobalamin deficiency).
Impaired absorption of vitamin B12 or inability to absorb it may lead to clinical symptoms when plasma levels fall below 200 pg/ml. The consequences include megaloblastic anemia and neurological deficits in the peripheral and central nervous system. Polyneuropathy may be present in combination with vertebral lesions and psychiatric disorders. Early symptoms of deficiency may include fatigue and pallor, tingling in the hands and feet, unsteady gait, and decreased muscle strength. Other neurological symptoms may occur, such as burning sensation, numbness, or pain in the hands and feet, muscle
weakness, confusion, and impaired judgment.
Symptoms caused by vitamin B12 deficiency can only be corrected by vitamin B12 intake. A therapeutic response to oral cyanocobalamin treatment should be evident within 2 months.
⚠️ Warnings
In cases of hematopoietic and/or neurological disorders, the following should be noted:
given the severity of the disease and possible consequences of an inadequate response, or if the patient
inadequately adheres to the treatment plan, the success of oral therapy must generally be carefully monitored.
It is recommended to check symptoms, reticulocyte counts, complete blood count
(including hemoglobin -Hb and hematocrit -Hk levels) and mean corpuscular volume seven days after initiating treatment. Thereafter, during the first 3 months, symptoms, blood count, and mean corpuscular volume should be monitored every 4 weeks, and if
patient compliance is good, subsequently at six-monthly/annual intervals. If non-compliance is suspected, more frequent monitoring may be necessary.
Caution is recommended in patients with folic acid deficiency. Folate deficiency may attenuate the therapeutic response. In these patients, the use of Vitamin B12 gamma should be accompanied by folate supplementation in consultation with a physician.
Since excess cyanocobalamin is excreted by the kidneys, vitamin B12 may
potentially accumulate, particularly in patients with end-stage renal disease (on dialysis). Serum vitamin B12 levels should be monitored regularly, and the treatment plan should be adjusted to maintain adequate serum vitamin B12 levels.
Due to the lack of pharmacokinetic, safety, and efficacy data in patients with hepatic impairment, careful patient monitoring may be necessary.
The product contains lactose. Patients with rare hereditary problems of galactose intolerance,
total lactase deficiency, or glucose-galactose malabsorption should not take this product.
The product contains sucrose. Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency should not take this product.
The product contains less than 1 mmol (23 mg) of sodium per tablet, that is to say it is essentially
"sodium-free".
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