Vitamin B12


Action And Clinical Pharmacology: Vitamin B is essential for growth, cell reproduction, hematopoiesis, nucleoprotein and myelin synthesis.

Within 48 hours after injection of 100 to 1 000 µg of vitamin B12, 50 to 98% of the injected dose may appear in the urine. The major portion is excreted within the first 8 hours.

Indications And Clinical Uses: For vitamin B12 deficiency occurring in: pernicious anemia with or without neurological complications. Other macrocytic, megaloblastic anemias where etiology suggests malabsorption of vitamin B12 such as following gastrectomy; gastric carcinoma; megaloblastic anemia associated with such gastrointestinal disorders as sprue syndrome, blind loops and anastomoses and fish tapeworm.

Note: In macrocytic megaloblastic anemia of pregnancy and sprue syndromes, cyanocobalamin may fail to produce satisfactory response, folic acid being indicated alone or in combination with cyanocobalamin.

The injection is also suitable for use as the flushing dose in the Schilling (vitamin B12 absorption) Test for pernicious anemia.

Contra-Indications: Sensitivity to cobalt or vitamin B12.

Manufacturers’ Warnings In Clinical States: Patients who have early Leber’s disease (hereditary optic nerve atrophy) have been found to suffer severe and swift optic atrophy when treated with vitamin B12.

Hypokalemia and sudden death may occur when severe megaloblastic anemia is treated intensively. Lack of therapeutic response may be due to infection, uremia, concomitant treatment with chloramphenicol or misdiagnosis.

Precautions: Before administering vitamin B12, an intradermal test dose is recommended for patients known to be sensitive to cobalamines.

Most antibiotics, methotrexate and pyrimethamine invalidate folic acid and vitamin B12 diagnostic microbiological blood assays.

Colchicine, para-aminosalicylic acid or excessive alcohol intake for longer than 2 weeks may produce malabsorption of vitamin B12. Doses of vitamin B12 exceeding 10 µg daily may produce a hematologic response in patients who have a folate deficiency.

Indiscriminate administration of vitamin B12 may mask the true diagnosis of pernicious anemia. A dietary deficiency of only vitamin B12 is rare. Multiple vitamin deficiency is expected in any dietary deficiency.

Adverse Reactions: Mild transient diarrhea, polycythemia vera, peripheral vascular thrombosis, itching, transitory exanthema, feeling of swelling of entire body, pulmonary edema and congestive heart failure early in treatment, anaphylactic shock and death have been reported following vitamin B12 administration.

Dosage And Administration: In patients with Addisonian (pernicious) anemia, parenteral therapy with vitamin B12 is the recommended method of treatment and will be required for the remainder of the patient’s life. Oral therapy is not dependable. Serum potassium must be watched closely the first 48 hours; and potassium should be replaced if necessary. Reticulocyte plasma count, vitamin B12 and folic acid levels must be obtained prior to treatment and between the fifth and seventh day of therapy.

In patients with other types of vitamin B12 deficiency due to malabsorption, the malabsorption should be corrected. In all patients a well balanced dietary intake should be prescribed and poor dietary habits should be corrected.

Treatment of vitamin B12 deficiency: 30 µg daily for 5 to 10 days followed by 100 µg monthly injected i.m. or deep s.c. Folic acid should be administered concomitantly early in the treatment unless folic acid levels are adequate.

Note: Cyanocobalamin should not be administered i.v.

Schilling Test: The flushing dose is 1 000 µg.

Availability And Storage: Each mL of clear, sterile, red aqueous solution for injection contains: vitamin B12 1 000 µg. Nonmedicinal ingredients: benzyl alcohol 1.5% w/v, sodium chloride, sodium hydroxide or hydrochloric acid (for pH adjustment) and water for injection. Vials of 10 mL. Store at room temperature. Protect from freezing, sunlight and excessive heat.

RUBRAMIN® Squibb Vitamin B12 Hematopoietic

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