Cyanocobalamin — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	SC or IM	250-500 µg/dog	q7d for 4 weeks, then monthly	Duration: Lifelong if deficiency is chronic Notes: For hereditary cobalamin malabsorption, higher doses may be needed (e.g., 1 mg/dog weekly).
Cat	SC or IM	250 µg/cat	q7d for 4 weeks, then monthly	Duration: Lifelong if deficiency is chronic Notes: For chronic enteropathies, some protocols use 250-500 µg weekly for 6 weeks, then monthly.
Horse	IM	5-10 mg/horse	q7d	Duration: As needed Notes: Often used as a tonic or for anemia; evidence of efficacy is limited.
Cattle	IM or SC	1-2 mg/animal	q7d	Duration: As needed Notes: For cobalt deficiency, address dietary cobalt.
Small Ruminants (Sheep/Goats)	IM or SC	0.5-1 mg/animal	q7d	Duration: As needed Notes: For cobalt deficiency, address dietary cobalt.
Rabbit	SC or IM	0.1-0.2 mg/kg	q7d	Duration: As needed Notes: Limited evidence; use with caution.
Bird/Poultry	IM or SC	0.05-0.1 mg/kg	q7d	Duration: As needed Notes: Limited evidence; use with caution.

Clinical Indications & Species Uses

General Indications

Vitamin B12 deficiency
Megaloblastic anemia
Neuropathies associated with B12 deficiency

Dog (Canine)

Treatment of vitamin B12 deficiency (e.g., due to exocrine pancreatic insufficiency, intestinal malabsorption, or hereditary selective cobalamin malabsorption)
Supportive therapy for anemia
Adjunct in the management of gastrointestinal disease

Cat (Feline)

Treatment of vitamin B12 deficiency (e.g., due to chronic enteropathies, exocrine pancreatic insufficiency, or intestinal lymphoma)
Supportive therapy for anemia
Adjunct in the management of gastrointestinal disease

Horse (Equine)

Treatment of vitamin B12 deficiency (rare, may occur with malabsorption or malnutrition)
Supportive therapy for anemia or neurologic conditions

Cattle (Bovine)

Treatment of vitamin B12 deficiency (e.g., cobalt deficiency)
Supportive therapy for anemia

Small Ruminants (Sheep / Goat)

Treatment of vitamin B12 deficiency (e.g., cobalt deficiency in sheep and goats)

Pharmacology & Mechanism of Action

Drug Class: Vitamin B12 | Pharmacological Group: Water-soluble vitamin

Mechanism of Action: Cyanocobalamin is a synthetic form of vitamin B12 that is converted in the body to the active coenzymes methylcobalamin and adenosylcobalamin. These coenzymes are essential for DNA synthesis, red blood cell formation, and neurological function. They act as cofactors for enzymes involved in the metabolism of amino acids, fatty acids, and carbohydrates, particularly in the conversion of methylmalonyl-CoA to succinyl-CoA and homocysteine to methionine. Deficiency leads to impaired cell division, megaloblastic anemia, and neurological degeneration.

Pharmacodynamics: Cyanocobalamin restores normal hematopoiesis and neurological function in vitamin B12 deficiency. It promotes the maturation of erythroblasts, maintains myelin sheath integrity, and supports the function of rapidly dividing cells such as bone marrow and gastrointestinal epithelium. It also plays a role in the synthesis of neurotransmitters and in the metabolism of folate.

⚡ Pharmacokinetics Summary

Absorption: Orally administered cyanocobalamin is absorbed in the ileum via intrinsic factor-dependent mechanism; however, in animals with gastrointestinal disease or after gastrectomy, absorption may be impaired. Parenteral administration (IM/SC) bypasses absorption issues and provides rapid elevation of serum B12 levels.

Distribution: Cyanocobalamin is widely distributed in the body, with high concentrations in the liver, kidneys, and heart. It crosses the placenta and is excreted in milk. It binds to plasma proteins (transcobalamins) for transport.

Metabolism: Cyanocobalamin is metabolized in the liver to its active coenzyme forms: methylcobalamin and adenosylcobalamin. The cyanide group is removed and excreted.

Excretion: Excreted primarily in the bile, with enterohepatic recirculation. A small amount is excreted in urine. In cases of high doses, urinary excretion increases.

Half-Life: The half-life in dogs is approximately 1-2 days for the free vitamin, but the body stores can last for months. In humans, the half-life is about 6 days (400 days in the liver).

Bioavailability: Oral bioavailability is low (1-2%) due to the need for intrinsic factor; parenteral administration provides 100% bioavailability.

Protein Binding: Approximately 90% bound to plasma proteins (transcobalamins).

Available Formulations & Strengths

Injectable Solution 1000 µg/mL, 5000 µg/mL (IM, SC)

Oral Tablet 100 µg, 500 µg, 1000 µg (PO)

Oral Liquid Various (PO)

Contraindications & Clinical Warnings

Contraindications:

Known hypersensitivity to cyanocobalamin or any component of the formulation
Leber's disease (hereditary optic nerve atrophy) in humans; not relevant in animals but caution in animals with similar conditions

Warnings & Clinical Precautions:

Use with caution in animals with renal impairment, as high doses may cause electrolyte imbalances.
Parenteral administration may cause pain at injection site.
Do not administer intravenously unless specified, as rapid administration may cause adverse reactions.
In food animals, observe withdrawal times.
Use in pregnant or lactating animals only if clearly needed; no known teratogenic effects.

Adverse Effects & Reactions

Common:

Pain at injection site
Mild transient diarrhea
Polycythemia (with excessive doses)

Serious / Severe:

Anaphylactic reactions (rare)
Hypokalemia (with rapid hematopoiesis)
Congestive heart failure (with prolonged high doses)

Rare:

Acneiform eruptions
Itching
Transient exanthema

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Chloramphenicol	May decrease the hematopoietic response to cyanocobalamin.	Moderate
Colchicine	May impair absorption of oral cyanocobalamin.	Moderate
Aminoglycosides	May reduce absorption of oral cyanocobalamin.	Mild
Potassium supplements	May decrease absorption of cyanocobalamin in the ileum.	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Polycythemia
Hypokalemia
Sodium retention
Edema
Congestive heart failure (with chronic high doses)

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Discontinue cyanocobalamin, monitor electrolytes, and provide cardiac support if needed. There is no specific antidote.

Food Animal Withdrawal Times

🥩 Meat: 0 days🥛 Milk: 0 days🥚 Eggs: 0 days

Cyanocobalamin is a vitamin and generally has zero withdrawal times, but always follow label or regulatory guidelines.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), protect from light.

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Do not freeze.

Dispensing Status: Over-The-Counter (OTC)

Approval Status: Approved for use in animals (e.g., as a veterinary injection) and also available as an OTC supplement.

Extra-Label (Off-Label) Use: Cyanocobalamin is not a prescription drug in most countries; however, extra-label use in food animals must comply with AMDUCA regulations in the US, requiring a valid VCPR and appropriate withdrawal times.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Cyanocobalamin is a safe and effective treatment for vitamin B12 deficiency in animals. It is commonly used in dogs and cats with chronic gastrointestinal disease, exocrine pancreatic insufficiency, or hereditary cobalamin malabsorption. Parenteral administration is preferred for reliable absorption. Monitoring serum cobalamin levels is recommended to guide dosing. In food animals, it is used to treat cobalt deficiency. Overall, it is well-tolerated with minimal adverse effects.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)