G-Vitamin B121 mg/ml

G-Vitamin B12 is a synthetic, biologically active form of vitamin B12 used to treat and prevent vitamin B12 deficiency and its consequences.

Established / FDA-approved uses

• Treatment of pernicious anemia (vitamin B12 deficiency due to lack of intrinsic factor)
• Treatment of vitamin B12 deficiency caused by malabsorption, including gastrointestinal surgery (e.g., gastrectomy, bariatric surgery), gluten-sensitive enteropathy (celiac disease), regional ileitis, or intestinal blind-loop syndrome
• Vitamin B12 deficiency due to fish tapeworm (Diphyllobothrium latum) infestation
• Vitamin B12 deficiency associated with pancreatic insufficiency or malignancy of the pancreas or bowel
• Nutritional (dietary) vitamin B12 deficiency, including in strict vegetarians/vegans
• Diagnostic aid in the Schilling test (flushing dose)

Guideline-supported / adjunct uses

• Vitamin B12–responsive megaloblastic anemia
• Neurological manifestations of B12 deficiency (e.g., peripheral neuropathy, subacute combined degeneration of the spinal cord) as part of correcting the underlying deficiency
• Prevention of B12 deficiency in conditions with chronically reduced absorption (e.g., long-term metformin or proton pump inhibitor use, atrophic gastritis)

G-Vitamin B12 is not indicated for conditions unrelated to true or at-risk vitamin B12 deficiency, and is not a general-purpose energy supplement.

Each formulation contains Cyanocobalamin as the active ingredient. In Bangladesh, Cyanocobalamin is commonly available as an injectable solution (intramuscular/subcutaneous) in strengths such as 250 mcg/mL and 1000 mcg/mL, and as oral tablets or drops in various strengths. Excipients vary by manufacturer and formulation.

G-Vitamin B12 is a stable, synthetic form of vitamin B12 (cobalamin), a water-soluble vitamin essential for normal red blood cell formation, DNA synthesis, and maintenance of the nervous system. Unlike naturally occurring cobalamins, G-Vitamin B12 contains a cyanide group bound to the cobalt atom; this bond is cleaved in the body to release the biologically active coenzyme forms (methylcobalamin and adenosylcobalamin).

G-Vitamin B12 is used therapeutically to correct vitamin B12 deficiency arising from inadequate dietary intake, impaired absorption (e.g., lack of intrinsic factor in pernicious anemia, gastrointestinal disease or surgery), or increased requirements.

Vitamin B12 (cobalamin) preparation; water-soluble vitamin / hematinic agent used in the management of G-Vitamin B12 deficiency states.

Cyanocobalamin is converted in the body to its active coenzyme forms, methylcobalamin and 5-deoxyadenosylcobalamin, which are required for two essential enzymatic reactions:

• Methionine synthase reaction: methylcobalamin acts as a cofactor for the conversion of homocysteine to methionine, which is also required to regenerate tetrahydrofolate for DNA synthesis. Deficiency impairs DNA synthesis in rapidly dividing cells, particularly bone marrow precursors, producing megaloblastic anemia.
• Methylmalonyl-CoA mutase reaction: adenosylcobalamin is required for conversion of methylmalonyl-CoA to succinyl-CoA, a step important in fatty acid metabolism and myelin synthesis. Deficiency here is linked to the neurological manifestations of B12 deficiency, including peripheral neuropathy and subacute combined degeneration of the spinal cord.

Absorption of oral Cyanocobalamin normally depends on intrinsic factor secreted by gastric parietal cells and an intact terminal ileum; at very high oral doses, a small fraction (about 1%) can be absorbed passively by simple diffusion, independent of intrinsic factor. Parenteral (injectable) Cyanocobalamin bypasses the need for intestinal absorption entirely and is used when malabsorption or intrinsic factor deficiency is present. Excess Cyanocobalamin is stored in the liver and excreted renally, largely unchanged.

• G-Vitamin B12 injection is given by intramuscular (IM) or deep subcutaneous (SC) injection; the intravenous route should be avoided as it results in rapid urinary loss of the vitamin and reduced efficacy.
• Oral G-Vitamin B12 tablets/drops may be taken with or without food, as directed.
• Do not administer G-Vitamin B12 injection if the solution is discolored or contains particulate matter.
• Because rare anaphylactic reactions have been reported with parenteral vitamin B12 products, an intradermal test dose may be considered in patients with suspected sensitivity, at the physician's discretion.

The following interactions with G-Vitamin B12 are clinically relevant:

• Chloramphenicol: may blunt the hematologic response to G-Vitamin B12 in some patients; monitor blood counts if co-administered.
• Metformin, proton pump inhibitors, and H2-receptor antagonists (e.g., cimetidine): long-term use reduces absorption of dietary/oral vitamin B12 and may increase the need for G-Vitamin B12 supplementation.
• Colchicine and prolonged heavy alcohol intake: can impair intestinal absorption of oral G-Vitamin B12.
• Aminosalicylic acid (para-aminosalicylic acid) and certain anticonvulsants: may reduce absorption of oral vitamin B12, potentially reducing effectiveness of G-Vitamin B12.
• Folic acid (high dose): can correct the megaloblastic anemia of B12 deficiency while allowing underlying neurological damage to progress if G-Vitamin B12 deficiency is not separately treated; see also Precautions.
• Laboratory/diagnostic interference: antibiotics, methotrexate, and pyrimethamine can invalidate microbiologic assays used to measure vitamin B12 levels, potentially confounding assessment of response to G-Vitamin B12.

Most people tolerate G-Vitamin B12 well. Reported adverse effects include:

• Common: pain, itching, or mild reaction at the injection site (parenteral use); mild diarrhea; headache; dizziness; feeling of swelling over the whole body.
• Less common: generalized itching; transient exanthema (skin eruptions); polycythemia vera unmasking in predisposed individuals.
• Rare but serious: hypersensitivity reactions including anaphylaxis and angioedema (more common with parenteral use); pulmonary edema and worsening of congestive heart failure early in treatment, related to rapid intracellular potassium shifts and volume expansion during hematologic response; peripheral vascular thrombosis.

Patients should seek prompt medical attention for signs of a severe allergic reaction (difficulty breathing, swelling of the face/throat, severe rash) during or after G-Vitamin B12 administration.

Pregnancy: G-Vitamin B12 is a normal nutritional requirement in pregnancy, and correcting a true deficiency is generally considered appropriate; however, robust controlled trial data on supplemental/pharmacologic G-Vitamin B12 use in pregnancy are limited. G-Vitamin B12 should be used in pregnancy only if clearly needed, at doses appropriate to correct documented deficiency, and under medical supervision — consult a physician before use.

Lactation: Vitamin B12 is excreted into breast milk. Use of G-Vitamin B12 to treat a documented maternal deficiency is generally considered appropriate and can help prevent infant B12 deficiency, but breastfeeding mothers should use G-Vitamin B12 only on medical advice, particularly at higher-than-nutritional doses.

• Masking of other conditions: G-Vitamin B12 may produce hematologic improvement in early pernicious anemia without addressing progression of the underlying disease; folate deficiency should also be considered, as folic acid alone can correct the megaloblastic anemia of B12 deficiency while neurological damage from the G-Vitamin B12 deficiency continues unchecked. Confirm the diagnosis before and during treatment, and treat concurrent folate deficiency appropriately.
• Leber's disease: avoid G-Vitamin B12 in hereditary optic neuropathy (see Contraindications).
• Hypokalemia and volume status: in patients with severe megaloblastic anemia, initiation of G-Vitamin B12 therapy can trigger a rapid increase in red cell production with a shift of potassium into cells, sometimes causing dangerous hypokalemia, and volume expansion that can worsen congestive heart failure or precipitate pulmonary edema; monitor potassium and cardiac status closely during early treatment of severe anemia.
• Hypersensitivity: rare anaphylactic reactions have occurred with parenteral vitamin B12; use with caution in patients with a history of allergic reactions to cobalamins.
• Diagnostic interference: G-Vitamin B12 therapy can interfere with certain vitamin B12 blood assays and microbiologic tests; inform the laboratory/physician if G-Vitamin B12 is being taken.
• Renal impairment: some parenteral formulations may contain aluminum; use with caution in patients with reduced renal function, especially with prolonged administration.

G-Vitamin B12 has a wide margin of safety, as excess vitamin B12 is generally excreted renally and significant toxicity from overdose has not been well documented. However, if an overdose of G-Vitamin B12 is suspected, or if signs of an allergic or unusual reaction occur after taking a larger-than-prescribed amount, seek immediate medical attention or contact a poison control center/emergency services rather than attempting to manage it at home.

Store G-Vitamin B12 at room temperature (20–25°C / below 30°C), protected from light, and away from moisture. Do not freeze injectable formulations. Keep out of reach of children.

• Pediatric use: G-Vitamin B12 is used for confirmed nutritional or malabsorptive vitamin B12 deficiency in children, with dosing individualized by age and severity; safety and efficacy of high-dose parenteral regimens have not been extensively established in children and should be supervised by a pediatrician.
• Elderly: vitamin B12 deficiency is common in older adults due to reduced gastric acid production and intrinsic factor; G-Vitamin B12 is commonly used in this population, with no specific dose adjustment required beyond individualizing to the degree of deficiency.
• Renal impairment: use with caution, particularly with prolonged parenteral therapy (see Precautions regarding aluminum content).
• Hepatic impairment: no well-established dose adjustment is required; use as clinically indicated.
• Leber's hereditary optic neuropathy: G-Vitamin B12 should not be used (see Contraindications).

Duration of G-Vitamin B12 therapy depends on the underlying cause. For irreversible causes of malabsorption (e.g., pernicious anemia, total gastrectomy), monthly maintenance G-Vitamin B12 injections are generally continued for life. For reversible or dietary deficiency, G-Vitamin B12 is typically continued until B12 levels and clinical/hematologic parameters normalize, then reassessed by the physician; some patients require ongoing lower-dose maintenance if the underlying risk factor persists.

Vitamins; Hematinics; Water-soluble (B-complex) vitamins; Cobalamins

Cyanocobalamin is converted intracellularly to its two active coenzyme forms: methylcobalamin, required by methionine synthase for the conversion of homocysteine to methionine (with concurrent regeneration of tetrahydrofolate needed for purine and thymidylate synthesis and hence DNA replication), and 5-deoxyadenosylcobalamin, required by methylmalonyl-CoA mutase for conversion of methylmalonyl-CoA to succinyl-CoA in fatty acid and amino acid metabolism, which is important for normal myelin formation. By restoring these coenzyme-dependent reactions, Cyanocobalamin corrects megaloblastic hematopoiesis and helps prevent or improve the neurological complications of vitamin B12 deficiency.

G-Vitamin B12 is used in children to treat confirmed nutritional vitamin B12 deficiency or deficiency due to malabsorption (e.g., congenital intrinsic factor deficiency, ileal disease). Oral doses of approximately 0.5–3 mcg daily are typical for dietary deficiency depending on age, while parenteral dosing for malabsorptive states is individualized by a pediatrician based on severity and response. Safety and efficacy of G-Vitamin B12 for indications beyond confirmed deficiency states have not been established in children, and G-Vitamin B12 should not be used in children with Leber's hereditary optic neuropathy.