Methylcobalamin Injection (Vitamin B12)

What is a Methylcobalamin Injection?

Methylcobalamin is a B-vitamin which is also known as Vitamin B12. It is found in food like meat, fish, shellfish and dairy products. Vitamin B12 is also present as Hydroxocobalamin and Cyanocobalamin and they can both be used as drug products. Methylcobalamin Injections are used to treat Vitamin B12 deficiency, pernicious anaemia and to determine some aspects of Vitamin B12 absorption in the Schilling test. Vitamin B12 is an essential Vitamin which is found in common food, so its deficiency in healthy individuals is very rare. Groups who are at a higher risk of developing a Vitamin B12 deficiency are the elderly, patients with malabsorption problems and very strict vegetarians. Vitamin B12 deficiency should be treated using Vitamin B12 supplements. If not treated early, it might lead to the development of anaemia, intestinal problems and irreversible damage to your nerves.

Methylcobalamin Chemical Structure

Methylcobalamin Chemical Structure

Methylcobalamin is a water-soluble organometallic compound with a trivalent cobalt ion bound inside a corrin ring. Even though it is similar to the porphyrin ring found in chlorophyll, heme and cytochrome, Methylcobalamin has its two pyrrole rings directly bound to each other making Cobalt (Co) the central metal ion. Plants and animals can not manufacture methylcobalamin. Only two organisms have the enzymes that are required for these processes, i.e. archaea and bacteria.

Mechanisms & Mode of Action of the Methylcobalamin Injection

Vitamin B12 in is assimilated in the body in two forms. These include; Methylcobalamin and 5-deoxyadenosyl cobalamin. Methylcobalamin acts as a cofactor of enzyme methionine synthase which is involved in the conversion of amino acid homocysteine into active methionine which is important for DNA methylation. The other form of Vitamin B12, 5-deoxyadenosyl cobalamin is also a co-factor which is essential to the enzyme that converts L-methylmalonyl-CoA into Succinyl-CoA. This conversion is very important since it facilitates the various processes which take part in the extraction of energy from fats and proteins in the body. Additionally, Succinyl-CoA is required in the production of haemoglobin, a substance found in the red blood cells that help it to carry and transport oxygen.

Methylcobalamin Chemical Structure

Methylcobalamin Chemical Structure

Methylcobalamin is also very crucial to the body in terms of growth, hematopoiesis, cell reproduction and the secretion of the myelin and nucleoproteins. The epithelial cells and the cells of the bone marrow are some sites which have the greatest requirement for methylcobalamin because they take part in rapid and continuous cell division. In tissues, Vitamin B12 is converted into coenzyme B12 which is essential for the conversion of methylmalonate to succinate and in the synthesis of methionine from homocysteine. This reaction requires folate. If the Vitamin B12 coenzyme is not available, tetrahydrofolate will not be synthesised from 5-methyltetrahydrofolate which often results in a folate deficiency. Vitamin B12 is also involved in maintaining sulfhydryl groups. Through its reactions, it facilitates the metabolism of fats, carbohydrates and the synthesis of proteins. With a vitamin B12 deficiency, individuals are at risk of acquiring megaloblastic anaemia, GI lesions and some neurological damages. The absorption of vitamin B12 into the bloodstream due to oral administration depends on an intrinsic factor, Without the intrinsic factor, a patient can also develop pernicious anaemia.

Pharmacokinetics of Methylcobalamin Vitamin B12

Vitamin B-12 in form of hydroxocobalamin can only be administered through intramuscular injections while methylcobalamin can be administered orally, intranasally and parenterally. After its absorption, Vitamin B-12 binds to transcobalamin II which is a carrier protein. This carrier protein transports and distributes it to the sites where it is required the most by the body. Some B12 is partially stored in the liver as a coenzyme B12 and other significant amounts stored in the bone marrow. This vitamin can cross over through a mother’s placenta to a foetus and it can also be distributed into breast milk. Vitamin B-12 has a lifetime of about 400 days in the liver. It is eliminated through the bile and the excess comes out as it is through the urine.

When administered intranasally or intramuscularly, Vitamin B12 is absorbed straight into the bloodstream where it performs its functions.

The possible side effects of Methylcobalamin B12 Injections

In many cases, methylcobalamin is not toxic even in large doses. The adverse side effects that have been reported from the administration of this medication include; headaches, paresthesias, nausea or vomiting, and rhinitis. Some reactions due to an intramuscular injection can include; mild diarrhoea, nervousness, anxiety, ataxia, pruritus and swelling of some parts or your whole body.

Congestive heart failure and pulmonary oedema are also some conditions that have been reported in early treatment periods using parenteral administration. This may be due to the high volume of blood that is produced by the action of methylcobalamin. It can also cause peripheral vascular thrombosis and angioedema and its related conditions.

Other Adverse reactions that are related to intranasal administration of this treatment can include; headaches, rhinorrhoea, dizziness, bronchitis, rashes, nasal discomfort, nasal pains, back pains, cough, asthma, hypersomnia, epistaxis, malaise, post nasal drips, procedural pains and tooth abseil.

You should always contact your physician immediately, in any case, you develop any signs of hypersensitive reactions to this medication. These can include; skin rashes, swelling of body parts, wheezing, chest tightness, difficulty in breathing and passing out.

Contraindications and Precauctions of Methylcobalamin Vitamin B12

You should never take the methylcobalamin medication if you have a hypersensitive reaction to methyl-cobalamin, cobalt and any other medical components present in this medication.

You should avoid methylcobalamin if you suffer from Leber’s disease, a hereditary optic nerve atrophy because this condition can worsen with an increase in methylcobalamin levels.

Methylcobalamin contains benzyl alcohol so you should be cautious in case you experience hypersensitive reactions to ethanol.

You should never use Folic acid, vitamin B-9 as a substitute for methylcobalamin, even though it has proven to improve some conditions of megaloblastic anaemia, the exclusive use of Vitamin B-9 for the treatment of this condition can result in irreversible and progressive damages to your neurons.

Certain medical conditions like renal failure, concurrent renal and hepatic diseases, serious medical infections and the use of drugs that suppress the activities of the bone marrow can interfere with the response of the body to the methylcobalamin treatment. If you suffer from these conditions, you might require higher doses during your treatment so that you can attain the normal levels and effects, however, this is not recommended.

Conclusive research has not been conducted and established on the effects of this treatment on pregnant and lactating women. Parenteral methylcobalamin is classified as pregnancy category C. So far, no maternal or foetal complications have been reported. When administered, Methylcobalamin is distributed in a mother’s breast milk in similar amounts to that in the plasma. This allows breastfeeding infants to take in adequate amounts of this vitamin into their bloodstream. This has its advantages since vitamin B-12 facilitates various functions in the body so its requirement increases substantially in lactating mothers. This benefits their infants too.

Clinical reports have not been done on various responses of this medication on the youth and the elderly, but its administration to elderly patients should be done with a lot of caution and monitoring.

There are numerous situations when you should completely avoid this medication or have it administered under strict monitoring. Always inform your health service provider of all the conditions or drugs that you are currently on so that you can avoid some negative effects.

Various interactions of the Methylcobalamin Injection include

There are numerous factors known to inhibit the effective absorption of methylcobalamin. Before you decide to begin with this treatment, inform your medical service provider of all the drugs, herbs, hereditary supplements and any other substances that you are on including any illegal drugs, alcohol and cigarettes. Some substances that might not interact well with methylcobalamin include;

– Drugs like para-aminosalicylic acid, colchicine, omeprazole and other proton pump inhibitors, chloramphenicol, anti-infective agents like pyrimethamine and any other medication that is known to suppress bone marrow activities, e.g. myelosuppressive antineoplastic agents.

Chloramphenicol is known to cause the suppression of the bone marrow. It can antagonise the hematopoietic response to Methylcobalamin, through its interference with erythrocyte maturation.

Hot food may cause nasal secretions and medication efficacy or a resulting loss of medication. Interactions between various food and oral or injectable forms of methylcobalamin are not expected.

– You should avoid heavy consumption of alcohol since ethanol can limit the absorption of Methylcobalamin.

What is the best method for the administration of Methylcobalamin Injection?

The way that has proven to be the most effective to administer this medication is through injections deep into the skin. You can do this by yourself but it is best to seek medical help and assistance from a qualified physician. If you ever happen to miss a dose. Reschedule your appointment as soon as possible or administer the treatment as soon as you can.

This medicine should be stored in a refrigerator below 41°F (5°C) and away from moisture and direct light. All medicine should be kept out of the reach of children. Throw away any unused medicine after the expiration date. Do not flush unused medications or pour down a sink or drain.

General Statements

Do not share or take anyone else’s medicine. Communicate with your healthcare provider before starting any new medicine, including over-the-counter, natural products, or vitamin supplements. This patient information summarizes the most important information about your medication; if you would like more information, Contact us immediately or communicate with your physician.


Methylcobalamin Injections (Vitamin B12) are commonly prescribed for:

Helping in the growth of healthy blood cells, nerve cells, and synthesis of proteins in the body. It also helps with metabolism of fats and carbohydrates and It is indicated as a treatment for people who cannot absorb Vitamin B12.

The dosage form available is an injection solution which is compounded under the stringent rules of USP 797 guidelines.

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