Vitamin B12 Depot

Uses

Vitamin B12 Depot is used for the treatment of known or suspected cyanide poisoning.

Identifying Patients with Cyanide Poisoning: Cyanide poisoning may result from inhalation, ingestion, or dermal exposure to various cyanide-containing compounds, including smoke from closed-space fires. Sources of cyanide poisoning include hydrogen cyanide and its salts, cyanogenic plants, aliphatic nitriles, and prolonged exposure to sodium nitroprusside.

The presence and extent of cyanide poisoning are often initially unknown. There is no widely available, rapid, confirmatory cyanide blood test. Treatment decisions must be made on the basis of clinical history and signs and symptoms of cyanide intoxication. If clinical suspicion of cyanide poisoning is high, Vitamin B12 Depot should be administered without delay.

In some settings, panic symptoms including tachypnea and vomiting may mimic early cyanide poisoning signs. The presence of altered mental status (e.g., confusion and disorientation) and/or mydriasis is suggestive of true cyanide poisoning although these signs can occur with other toxic exposures as well.

Smoke Inhalation: Not all smoke inhalation victims will have cyanide poisoning and may present with burns, trauma, and exposure to other toxic substances making a diagnosis of cyanide poisoning particularly difficult. Prior to administration of Vitamin B12 Depot, smoke-inhalation victims should be assessed for the following:

• Exposure to fire or smoke in an enclosed area
• Presence of soot around the mouth, nose or oropharynx
• Altered mental status

Although hypotension is highly suggestive of cyanide poisoning, it is only present in a small percentage of cyanide-poisoned smoke inhalation victims. Also indicative of cyanide poisoning is a plasma lactate concentration ≥ 10 mmol/L (a value higher than that typically listed in the table of signs and symptoms of isolated cyanide poisoning because carbon monoxide associated with smoke inhalation also contributes to lactic acidemia). If cyanide poisoning is suspected, treatment should not be delayed to obtain a plasma lactate concentration.

Use with Other Cyanide Antidotes: Caution should be exercised when administering other cyanide antidotes simultaneously with Vitamin B12 Depot, as the safety of co-administration has not been established. If a decision is made to administer another cyanide antidote with Vitamin B12 Depot, these drugs should not be administered concurrently in the same intravenous line.

Vitamin B12 Depot is also used to associated treatment for these conditions: Anemia, Pernicious, B Vitamin Deficiency, Toxic effect of hydrocyanic acid and cyanides, Vitamin B12 Deficiency

How Vitamin B12 Depot works

Vitamin B12 exists in four major forms referred to collectively as cobalamins; deoxyadenosylcobalamin, methylcobalamin, hydroxocobalamin, and cyanocobalamin. Two of these, methylcobalamin and 5-deoxyadenosyl cobalamin, are primarily used by the body. Methionine synthase needs methylcobalamin as a cofactor. This enzyme is involved in the conversion of the amino acid homocysteine into methionine. Methionine in turn is required for DNA methylation. 5-Deoxyadenosyl cobalamin is a cofactor needed by the enzyme that converts L-methylmalonyl-CoA to succinyl-CoA. This conversion is an important step in the extraction of energy from proteins and fats. Furthermore, succinyl CoA is necessary for the production of hemoglobin, the substances that carries oxygen in red blood cells.

Dosage

Vitamin B12 Depot dosage

Thirty mcg daily for 5 to 10 days followed by 100 to 200 mcg monthly injected intramuscularly. If the patient is critically ill, or has neurologic disease, an infectious disease or hyperthyroidism, considerably higher doses may be indicated. However, current data indicate that the optimum obtainable neurologic response may be expected with a dosage of vitamin B12 sufficient to produce good hematologic response. Children may be given a total of 1 to 5 mg over a period of 2 or more weeks in doses of 100 mcg, then 30 to 50 mcg every 4 weeks for maintenance.

Side Effects

Mild transient diarrhea, itching, transitory exanthema, feeling of swelling of entire body, and anaphylaxis. A few patients may experience pain after injection of hydroxocobalamin.

Precaution

The validity of diagnostic vitamin B12 or folic acid blood assays could be compromised by medications, and this should be considered before relying on such tests for therapy.

Vitamin B12 is not a substitute for folic acid and since it might improve folic acid deficient megaloblastic anemia, indiscriminate use of vitamin B12 could mask the true diagnosis.

Hypokalemia and thrombocytosis could occur upon conversion of severe megaloblastic to normal erythropoiesis with B12 therapy. Therefore, serum potassium levels and the platelet count should be monitored carefully during therapy.

Vitamin B12 deficiency may suppress the signs of polycythemia vera. Treatment with vitamin B12 may unmask this condition.

Interaction

• history of interaction with ARI Sodium Iodide (II23) 1 -12 MBq (sodium iodide i-123)
• ARI Sodium Iodide (1123) 100-750 MBq (sodium iodide i-123) arsenic trioxide
• Chloracol (chloramphenicol) chloramphenicol
• Chloromycetin (chloramphenicol)
• Chloromycetin Sodium Succinate (chloramphenicol)
• Hicon (sodium iodide-i-131) lodotope (sodium iodide-i-131) sodium iodide i-123 sodium iodide-i-131 Trisenox (arsenic trioxide)

Food Interaction

Vitamin B12 Depot Disease Interaction

Major: hypokalemia, optic nerveModerate: malabsorption

Elimination Route

Readily absorbed from the gastrointestinal tract, except in malabsorption syndromes. Vitamin B12 is absorbed in the lower half of the ileum.

Half Life

Approximately 6 days (peak plasma concentration after 8-12 hours from oral administration)

Elimination Route

Each hydroxocobalamin molecule can bind one cyanide ion by substituting it for the hydroxo ligand linked to the trivalent cobalt ion, to form cyanocobalamin, which is then excreted in the urine.

Pregnancy & Breastfeeding use

Pregnancy Category C. Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks

Contraindication

Hypersensitivity to any component of this medication.

Storage Condition

Should be stored in cool and dry place

Innovators Monograph

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