OB-GYN 101
Pharmacy

Contents  ·  Introduction  ·  Learning Objectives  ·  Clinical Issues  ·  Procedures  ·  Library  ·  Pharmacy  ·  Lab  ·  Chest X-ray  ·  Ultrasound  ·  Videos  ·  Forms  ·  Progress Notes  ·  Facts Cards  ·  Students  ·  Search  ·  Feedback  ·  About Us

 

 

Vitamin B12 (Cyanocobalamin)

Category:

  • Vitamin

Description:

  • Dietary supplement; water-soluble vitamin

Indications:

  • Vitamin B12 deficiency

    • necessary for bone marrow and proper CNS and GI function

  • Pernicious anemia (enlarged (macrocytic) red blood cells)

  • Increased vitamin B12 requirements: 

    • Pregnancy

    • Thyrotoxicosis

    • Hemolytic anemia

    • Hemorrhage

    • Malignancies

    • Hepatic or renal disease.

  • Unlabeled uses:

    • cyanide toxicity associated with sodium nitroprusside.  Vitamin B12 binds with free cyanide to form cyanocobalamin and thereby decreasing RBC and plasma cyanide concentrations.

Contraindications:

  • Sensitivity to cobalt

Precautions:

  • Pregnancy category C

  • Vitamin B12 deficiency is related to malabsorption syndrome seen in patients with:

    • Pernious anemia

    • GI pathology, dysfunction or surgery, 

    • Tapeworm infestation

    • Pancreatic or bowel malignancies

    • Sprue

    • Small bowel bacterial overgrowth

    • Gastrectomy

    • Folic acid deficiency.

  • If the patient exhibits an inadequate response, it may be due to:

    • Infection

    • Uremia

    • Bone marrow suppressive medications

    • Concurrent iron or folic acid deficiency

    • Misdiagnosis.

  • Patients with Leber’s disease (hereditary optic nerve atrophy) suffer severe and swift optic nerve atrophy.

  • Long-term vitamin B12 deficiency may produce permanent degenerative lesions on the spinal cord.

  • Give a test dose of parenteral vitamin B12 due to cases of anaphylactic reactions.

  • Vitamin B12 deficiency is common in immunocompromised patients, monitor AIDS and HIV patients vitamin B12 levels.

  • The maximum amount of vitamin B12 absorbed per dose is 1-5mcg and the percentages decreases with subsequent doses.

Adverse Reactions (Side Effects):

  • Relatively non-toxic in therapeutic doses

  • Parenteral vitamin B12:

    • Cardiovascular: pulmonary edema, congestive heart failure in early treatment, peripheral vascular thrombosis

    • Itching, transitory exanthema

    • Feeling of generalized body swelling, mild transient diarrhea, injection site pain

 

 

Dosage:

  • Dietary sources: meat products (produced by microorganisms in animal proteins), dairy products

  • Administered in oral tablets, intranasal gel and injectable

  • Dietary supplementation (RDA: recommended daily allowance):

    • Adults: 2 mcg per day

  • Normal dosing:

    • oral: up to 1000mcg per day

    • parenteral: IM or SQ: 30mcg per day for 3-10 days, then followed by 100-200mcg on a monthly basis

  • Addisonian pernious anemia:

    • IV therapy is required for life

    • 100mcg per day for 6-7 days by deep IM or SQ injection

    • if improvement occurs, give every other day for 2 weeks, then every 3-4 days for another 2-3 weeks, then 100mcg per day for remainder of life

 

The information contained here is an abbreviated summary. For more detailed and complete information, consult the manufacturer's product information sheets or standard textbooks.

Source: Operational Medicine 2001,  Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300

OB-GYN 101: Introductory Obstetrics & Gynecology
© 2003, 2004, 2005, 2008 Brookside Associates, LLC
All rights reserved

Advertise on this site