PRECAUTIONS
General Precautions
Vitamin B12 deficiency that is allowed to progress for longer than 3 months
may produce permanent degenerative lesions of the spinal cord. Doses of folic
acid greater than 0.1 mg per day may result in hematologic remission in patients
with vitamin B12 deficiency. Neurologic manifestations will not be prevented
with folic acid, and if not treated with vitamin B12, irreversible damage will
result.
Doses of cyanocobalamin exceeding 10 mcg daily may produce hematologic response in patients with folate deficiency. Indiscriminate administration may mask the true diagnosis.
Laboratory Tests
During the initial treatment of patients with pernicious anemia, serum potassium
must be observed closely the first 48 hours and potassium replaced if necessary.
Hematocrit, reticulocyte count, vitamin B12, folate and iron levels should be obtained prior to treatment. Hematocrit and reticulocyte counts should be repeated daily from the fifth to seventh days of therapy and then frequently until the hematocrit is normal. If folate levels are low, folic acid should also be administered. If reticulocytes have not increased after treatment or if reticulocyte counts do not continue at least twice normal as long as the hematocrit is less than 35%, diagnosis or treatment should be reevaluated. Repeat determinations of iron and folic acid may reveal a complicating illness that might inhibit the response of the marrow.
Patients with pernicious anemia have about 3 times the incidence of carcinoma of the stomach as the general population, so appropriate tests for this condition should be carried out when indicated.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long term studies in animals to evaluate carcinogenic potential have not been
done. There is no evidence from long-term use in patients with pernicious anemia
that cyanocobalamin is carcinogenic. Pernicious anemia is associated with an
increased incidence of carcinoma of the stomach, but this is believed to be
related to the underlying pathology and not to treatment with cyanocobalamin.
Pregnancy: Teratogenic Effects
Pregnancy Category C: Adequate and well-controlled studies have not
been done in pregnant women. However, vitamin B12 is an essential vitamin and
requirements are increased during pregnancy. Amounts of vitamin B12 that are
recommended by the Food and Nutrition Board, National Academy of Science-National
Research Council for pregnant women (4 mcg daily) should be consumed during
pregnancy.
Nursing Mothers
Vitamin B12 is known to be excreted in human milk. Amounts of vitamin B12 that
are recommended by the Food and Nutrition Board, National Academy of Science-National
Research Council for lactating women (4 mcg daily) should be consumed during
lactation.
Pediatric Use
Intake in children should be in the amount (0.5 to 3 mcg daily) recommended
by the Food and Nutrition Board, National Academy of Science-National Research
Council.