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Methycobal® is a mecobalamin preparation for treatment of peripheral neuropathies. Methycobal® contains mecobalamin, a vitamin B12 coenzyme that occurs in the blood and the cerebrospinal fluid. It is taken up by nerve tissues more actively and extensively than other homologue of vitamin B12. Biochemically, Methycobal® accelerates the metabolic pathways of nucleic acids, proteins and lipids through its involvement in the transmethylation reaction. Thus, it exerts a repairing effect on injured nerve tissues. Clinically, Methycobal® is the first pharmaceutical product that has been shown, by double-blind clinical studies, to be effective and useful for the treatment of numbness, pain, and paralysis due to peripheral neuropathies such as Diabetic Neuropathy and Carpal Tunnel Syndrome.

Methycobal®

Methycobal® Tablets

Indication

Peripheral neuropathies

Dosage & Administration

Oral dosage: 1500µg daily in 3 divided doses, dosage may be adjusted depending on patient’s age and symptoms.

Pharmacodynamics

  1. Promotion of the metabolism of nucleic acids, proteins and lipids In an experiment using brain-derived cell strains obtained from albino rats, mecobalamin acted as a co-enzyme in methionine synthesis from homocysteine. In particular, it was found to be involved in the synthesis of thymidine from deoxyuridine and to accelerate the synthesis of DNA and RNA. In another experiment using neuroglia cells, mecobalamin was found to accelerate the synthesis of lecithin, a major component of the myelin sheath.
  2. Extensive uptake by nerve tissues and improvement of metabolic disturbances Mecobalamin, a methylated form of vitamin B12 (CH3-B12) that occurs in high concentrations in blood and cerebrospinal fluid has been observed in rats to be taken up into nerve cell organelles more actively and extensively than CN-B12. Experimentation using sciatic nerve cells from rats with experimental diabetes has also demonstrated that mecobalamin helps maintain axonal function by promoting the synthesis of structural proteins and by normalizing the transport velocity of these proteins.
  3. Repair of nerve injury Mecobalamin has been demonstrated, by neuropathological and electrophysiological studies, to inhibit nerve fiber degeneration in rats and rabbits with neuropathy induced by drugs such as adriamycin and vincristine or with streptozotocin–induced diabetes. The effects of mecobalamin were also studied in guinea pig models with compression-induced facial palsy. The recovery process was evaluated using examinations of the blink reflex, evoked eletromyograms, and histological observations. Mecobalamin was found to be as effective as steroids in accelerating the repair of injured nerve tissue.

Adverse Reactions and Precautions

Adverse reactions were reported in 146 out of 15,180 patients (0.96%).The most common adverse reactions include gastrointestinal symptoms such as anorexia in 52 patients (0.34%), gastrointestinal disorders in 38 patients (0.25%), nausea/vomiting in 18 patients (0.18%), diarrhea in 17 patients (0.11%), and skin rash in 14 patients (0.09%). General Precautions: Methycobal® should not be administered for extensive periods (months) to patients who show no clinical response. Other Precautions: Prolonged use of larger doses of Methycobal® is not recommended for patients whose occupation requires handling mercury or its compounds.

Methycobal® Injection

Indication

Peripheral neuropathies Megaloblastic anemia caused by vitamin B12 deficiency

Dosage & Administration

Injection: 500µg (1 ampule) three times a week, dosage may be adjusted depending on patient’s age and symptoms.

Pharmacology

  1. Mecobalamin is a kind of endogenous coenzyme B12. Mecobalamin plays an important role in transmethylation as a coenzyme of methionine synthetase in the synthesis of methionine from homocysteine.
  2. Mecobalamin is well transported to nerve cell organelles, and promotes nucleic acid and protein synthesis. Mecobalamin is better transported to nerve cell organelles than cyanocobalamin in rats. It has been shown in experiments with cells from the brain origin and spinal nerve cells in rats to be involved in the synthesis of thymidine from deoxyuridine, promotion of deposited folic acid utilization and metabolism of nucleic acid. Also, mecobalamin promotes nucleic acid and protein synthesis in rats more than cobamamide does.
  3. Mecobalamin promotes axonal transport and axonal regeneration. Mecobalamin normalizes axonal skeletal protein transport in sciatic nerve cells from rat models with streptozotocin-induced diabetes mellitus. It exhibits neuropathologically and electrophysiologically inhibitory effects on nerve degeneration in neuropathies induced by drugs, such as adriamycin, acrylamide, and vincristine (in rats and rabbits), models of axonal degeneration in mice and neuropathies in rats with spontaneous diabetes mellitus.
  4. Mecobalamin promotes myelination (phospholipid synthesis). Mecobalamin promotes the synthesis of lecithin, the main constituent of medullary sheath lipid and increases myelination of neurons in rat tissue culture more than cobamamide does.
  5. Mecobalamin restores delayed synaptic transmission and diminished neurotransmitters to normal. Mecobalamin restores end-plate potential induction early by increasing nerve fiber excitability in the crushed sciatic nerve in rats. In addition, mecobalamin normalizes diminished brain tissue levels of acetylcholine in rats fed a choline-deficient diet.
  6. Mecobalamin promotes the maturation and division of erythroblasts, thereby alleviating anemia. It is well known that vitamin B12-deficiency may cause specific megaloblastic anemia. Mecobalamin promotes nucleic acid synthesis in bone marrow and promotes the maturation and division of erythroblasts, thereby increasing erythrocyte production. Mecobalamin brings about a rapid recovery of diminished red blood cell, hemoglobin, and hematocrit in vitamin B12-deficient rats.

Adverse Reactions and Precautions:

Adverse reactions were reported in 13 of 2,872 patients (0.45%)

1)   Clinically significant adverse reactions (incidence unknown)
Anaphylactoid reactions
Anaphylactoid reaction such as decrease in blood pressure or dyspnea may occur. Patients should be carefully observed. In the event of such symptoms, treatment should be discontinued immediately and appropriate measures taken.
2)    Other adverse reactions
<0.1% Incidence unknown
Hypersensitivitynote Rash
Others Headache and hot sensation Diaphoresis and pain/ induration at the site of intramuscular injection

Note: In the event of such symptoms, treatment should be discontinued For further product information kindly refer to the prescribing information.

  Reference Methycobal® product insert.