Cyanocobalamin

BRAND NAMES

• Nascobal

• Rubramin

• Dodex

• Cyanoject

• Cobalin

• Vibecol

• Bevidox

MECHANISM OF ACTION

Cyanocobalamin works by converting in the body into active vitamin B12 forms (methylcobalamin and adenosylcobalamin), which act as essential cofactors for enzymes involved in DNA synthesis and energy metabolism. This helps restore normal red blood cell production and supports nerve function, thereby treating the effects of Vitamin B12 deficiency.

PHARMACOKINETICS

Absorption

Cyanocobalamin is absorbed mainly in the terminal ileum after binding to intrinsic factor, a protein produced in the stomach that protects vitamin B12 and helps its transport. A small amount can also be absorbed passively without intrinsic factor when given in high doses, which is useful in treating Vitamin B12 deficiency.

Distribution

Cyanocobalamin is transported in the blood bound to transcobalamin II and is widely distributed, with the highest storage in the liver. It is slowly released from body stores to support red blood cell formation and nerve function in Vitamin B12 deficiency.

Metabolism

Cyanocobalamin is converted in the body into its active forms, methylcobalamin and adenosylcobalamin, which are used in essential metabolic reactions like DNA synthesis and energy production. Any excess is stored mainly in the liver for future use, helping maintain vitamin B12 levels and prevent Vitamin B12 deficiency.

Elimination

Cyanocobalamin is mainly eliminated through bile, with most of it being recycled back into the body via enterohepatic circulation. Only a small amount is lost in urine, as the body efficiently conserves vitamin B12 to maintain normal levels and prevent Vitamin B12 deficiency.

PHARMACODYNAMICS

Cyanocobalamin acts as a vitamin B12 prodrug that is converted into its active forms, methylcobalamin and adenosylcobalamin, which function as essential cofactors in cellular metabolism. Its pharmacodynamic effects include supporting DNA synthesis, promoting normal red blood cell maturation, and maintaining myelin integrity in the nervous system. Through these actions, it helps correct the hematologic and neurological abnormalities seen in Vitamin B12 deficiency.

ADMINISTRATION

Cyanocobalamin is administered orally, intramuscularly (IM), subcutaneously, or intranasally depending on the severity of Vitamin B12 deficiency. Oral therapy is commonly used for mild deficiency, while IM injections are preferred in cases of malabsorption or severe deficiency to rapidly restore vitamin B12 levels. Intranasal forms are used for maintenance therapy after initial correction.

DOSAGE AND STRENGTH

Cyanocobalamin is available in several strengths depending on route of administration. Common oral doses include 100 mcg, 500 mcg, 1000 mcg, and 2000 mcg tablets/capsules, while intramuscular injections are typically available as 1000 mcg/mL (1 mg/mL) for treatment of Vitamin B12 deficiency. Intranasal formulations are usually provided as 500 mcg per spray, used for maintenance therapy after correction of deficiency.

DRUG INTERACTIONS

Cyanocobalamin can have reduced absorption when used with drugs like metformin and proton pump inhibitors, while chloramphenicol may reduce its hematologic response. These interactions may affect treatment outcomes in Vitamin B12 deficiency.

FOOD INTERACTIONS

Cyanocobalamin has minimal direct food interactions, but its absorption depends on normal gastric function. Foods that are naturally rich in vitamin B12, such as meat, fish, eggs, and dairy, do not interfere and may support overall intake. However, long-term strict vegan diets without supplementation can worsen deficiency in Vitamin B12 deficiency.

CONTRAINDICATIONS

Cyanocobalamin is contraindicated in patients with hypersensitivity to vitamin B12 or cobalt and should be avoided in those with Leber’s hereditary optic neuropathy. It is generally not used unless needed for treating Vitamin B12 deficiency.

SIDE EFFECTS

• Headache

• Nausea

• Diarrhea

• Dizziness

• Injection site pain, redness, or swelling

OVER DOSE

Cyanocobalamin overdose is rare and usually not serious because excess vitamin B12 is excreted in urine. Mild symptoms like nausea, diarrhea, headache, or skin rash may occur in some cases.

TOXICITY

Cyanocobalamin has very low toxicity, as excess amounts are usually excreted in urine and do not accumulate in the body. Serious toxic effects are rare, though mild hypersensitivity reactions may occasionally occur.