NEUROBION TABLET (OTC)

CYANOCOBALAMIN
PYRIDOXINE
THIAMINE DISULPHIDE

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

Cyanocob(III)alamin | Vitamin B12 | Vitamin B12 complex | Vitamin B12 NOS | Cyanocobalamin |

Description

Cyanocobalamin (commonly known as Vitamin B12) is the most chemically complex of all vitamins. Its chemical structure is based on a _corrin_ ring, which, although quite similar to the porphyrin ring found in heme, chlorophyll, and cytochrome, has two of the pyrrole rings directly bonded. The central metal ion in cyanocobalamin is Co (cobalt). Cyanocobalamin (Vitamin B12) is not produced by plants or by animals. The only organisms that have the enzymes required for the synthesis of cyanocobalamin are bacteria and archaea [L2058]. Higher plants do not utilize cyanocobalamin from the soil, and are therefore a poor source of the substance as compared with animal tissues, which are potent in cyanocobalamin [L2058]. Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods, but fortified breakfast cereals are a readily available source of vitamin B12 with high bioavailability for vegetarian consumers. Various nutritional yeast products also contain vitamin B12 [L2064]. The main causes of vitamin B12 deficiency include vitamin B12 malabsorption, pernicious anemia, postsurgical malabsorption, and lastly, dietary deficiency. In many cases, however, the cause of deficiency is unknown [L2064].

Indication

For treatment of pernicious anemia (due to lack of or inhibition of intrinsic factor) and for prevention and treatment of vitamin B 12 deficiency [L2064], [L2068]. Values below approximately 170–250 pg/mL (120–180 picomol/L) for adults suggest a vitamin B12 deficiency. Despite this, evidence suggests that serum vitamin B12 concentrations may not accurately reflect intracellular concentrations of the vitamin [L2064]. It is therefore difficult to diagnose vitamin B12 deficiency.

Mechanism of Action

Vitamin B12 is used in the body in two forms: Methylcobalamin and 5-deoxyadenosyl cobalamin. The enzyme methionine synthase needs methylcobalamin as a cofactor. This enzyme is involved in the conversion of the amino acid homocysteine into methionine. Methionine, is required for DNA methylation [L2064], [L2068]. Vitamin B12 is converted to coenzyme B12 in tissues. This form is required for the conversion of methylmalonate to succinate and the synthesis of methionine from homocysteine (a reaction also requiring folate) [L2068]. Without coenzyme B12, tetrahydrofolate cannot be regenerated from its inactive storage form, _5-methyl tetrahydrofolate_, leading to functional folate deficiency. Vitamin B12 also may be involved in maintaining sulfhydryl (SH) groups in the reduced form needed by many SH-activated enzyme systems [L2068]. Via the above reactions, vitamin B12 is associated with both fat and carbohydrate metabolism, as well as protein synthesis [L2068]. _5-Deoxyadenosyl_ cobalamin is a cofactor needed by the enzyme that acts to convert _L-methylmalonyl-CoA_ to _succinyl-CoA_. This conversion is an important step in the extraction of energy from proteins and fats. Additionally, _succinyl CoA_ is necessary for the production of hemoglobin, the substance that carries oxygen in red blood cells [L2064]. _L-methylmalonyl-CoA mutase_ converts L-methylmalonyl-CoA to succinyl-CoA in the degradation of propionate, an important biochemical reaction in the metabolism of lipids and proteins. _Succinyl-CoA_ is also required for hemoglobin synthesis [L2064].

Pharmacodynamics

Vitamin B12, or _methylcobalamin_, is imperative for growth, cell reproduction, hematopoiesis, and nucleoprotein and myelin synthesis. Cells which undergo rapid division (epithelial cells, bone marrow, myeloid cells) have the greatest requirement for methylcobalamin [L2068]. Cyanocobalamin (Vitamin B12) is a water-soluble organometallic compound with a trivalent cobalt ion bound inside a corrin ring. It is required for nerve cells and red blood cells, and to form DNA. Vitamin B12 deficiency is the cause of various forms of anemia [L2068]. Vitamin B12 deficiency results in megaloblastic anemia, gastrointestinal lesions, and neurologic damage (due to lack of myelin). Vitamin B12 requires an intrinsic factor-mediated active transport for absorption. Lack of or the inhibition of intrinsic factor may result in pernicious anemia [L2068]. Pernicious anemia is an autoimmune disease which damages the gastric mucosa, resulting in gastric atrophy. This leads to damage of the stomach parietal cells, achlorhydria (lack of gastric acid secretion), and failure to produce intrinsic factor, resulting in vitamin B12 malabsorption [L2068]. If pernicious anemia is not treated, it leads to vitamin B12 deficiency, eventually leading to megaloblastic anemia and neurological disorders, despite adequate dietary intake of vitamin B12 [L2064].

Pharmacokinetics

Absorption:

Approximately 56% of a 1 mcg oral dose of vitamin B12 is absorbed, however, absorption decreases significantly when intrinsic factor capacity is exceeded (at 1–2 mcg of vitamin B12) [L2064]. Readily absorbed in the lower half of the ileum [L2067]. Bioavailability of the nasal gel vitamin B12 and spray forms compared to intramuscular injection are about 9% and 6%, respectively [L2068]. Because the intranasal forms have lower absorption than the IM dosage form, intranasal B12 forms dosed administered once weekly. After 1 month of treatment in pernicious anemia, the weekly dosing of 500 mcg B12 intranasal gel resulted in a significant increase in B12 levels in comparison to a once-monthly 100 mcg IM dose [L2068].

Distribution:

Once absorbed, vitamin B12 is highly bound to transcobalamin II, a specific B-globulin carrier protein and is distributed and stored primarily in the liver as coenzyme B12 [L2068]. It has been found that the distribution of vitamin B12 is dependent on the current cobalamine status, from animal studies [L2067]. The bone marrow also stores a high amount of absorbed vitamin B12 [L2068]. This vitamin crosses the placenta and is found distributed in breast milk. Enterohepatic recirculation conserves systemic stores of Vitamin B12 [L2067].

Metabolism:

Mainly Hepatic [A32397], [L2058]. Vitamin B12 serves as a cofactor for methionine synthase and _L-methylmalonyl-CoA mutase_ enyme. Methionine synthase catalyzes the conversion of homocysteine to methionine during metabolism. Methionine is necessary for the formation of S-adenosylmethionine, a universal methyl donor for about 100 substrates, including DNA, RNA, hormones, proteins, and lipids [L2064]. Vitamin B12, which is bound to protein in food, is released following the activity of hydrochloric acid and gastric protease in the stomach. When synthetic vitamin B12 is added to fortified foods and dietary supplements, it is found in the free form and, and does not require this separation step. Free vitamin B12 then binds with intrinsic factor (IF), a glycoprotein secreted by the parietal cells of the stomach, and the newly formed complex undergoes absorption within the distal ileum by receptor-mediated endocytosis [L2071]. Intestinal microorganisms produce cobalamin in the colon, however, not absorbed and thus vitamin B12 must be supplied with the food. In mammals, the assimilation and transport of dietary cobalamin is performed by three successive proteins, haptocorrin (HC), gastric intrinsic factor (IF) and transcoba- lamin. Cobalamin is required by cells for two enzyme cofactors, _methyl-Cbl_ for _methionine synthase_ and _50 -deoxyadenosyl-Cbl (Ado-Cbl)_ for _methyl- malonyl-CoA mutase_ [L2068]. In the stomach, Cobalamin is firstly bound to salivary HC. Following proteolytic cleavage of HC into 2-3 fragments in the duodenum, and is then transferred to IF. Mucosal cells in the terminal ileum absorb the IF-Cobalamin complex by a process called _endocytosis_ by the _cubilin_-amnionless receptor [L2068]. In the enterocyte (intestinal cell), Cobalamin is freed from IF and appears in the blood combined with transcobalamin which carries cobalamin to cells. Only the fraction of Cbl bound to TC is quickly taken up by endocytosis by a specific receptor of yet unknown structure, present on most cell types [L2068]. The other Cbl- transporting protein in plasma is homocysteine. Its ability to promote cellular uptake of cobalamin is found to be limited, but it is thought to serve as a storage protein as well as scavenger of inactive Cbl- analogues [L2071].

Elimination:

In healthy individuals receiving only dietary vitamin B12, approximately 3 - 8 micrograms (mcg) of the vitamin is secreted into the GI tract daily, primarily from bile. Most excreted, however, 1 mcg is reabsorbed; less than 0.25 mcg is usually excreted in the urine daily. When vitamin B12 is administered in amounts that exceed the binding capacity of plasma, the liver, and other tissues, it’s free in the blood for urinary excretion [L2072].

Half-life

Approximately 6 days (400 days in the liver) [L2058]

Clearance

Not Available

Toxicity

Anaphylactic reactions (skin rash, itching, wheezing) post parenteral administration has occurred. The Institute of Medicine (IOM), USA, did not establish an upper limit for vitamin B12 because of its low potential for toxicity. In Dietary Reference Intakes [L2066]: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline, the IOM declares that “no adverse effects have an association with excess vitamin B12 intake from both food and dietary supplements in healthy individuals” [L2066]. Findings from intervention trials support these conclusions. In the NORVIT and HOPE 2 trials, vitamin B12 supplementation (in combination with folic acid and vitamin B6) did not cause any serious adverse events when administered at doses of 0.4 mg for 40 months (NORVIT trial) and 1.0 mg for 5 years (HOPE 2 trial) [A32388, A32389]. Parenteral methylcobalamin is classified as pregnancy category C. Adequate studies in humans have not been conducted; however, no maternal or fetal complications have been associated with doses that are recommended during pregnancy, and appropriate treatment should not be withheld from pregnant women with vitamin B12 responsive anemias. Conversely, pernicious anemia resulting from vitamin B12 deficiency may cause infertility or poor pregnancy outcomes. Vitamin B12 deficiency has occurred in breast-fed infants of vegetarian mothers whose diets contain no animal products (e.g., eggs, dairy), even though the mothers had no symptoms of deficiency at the time. Maternal requirements for vitamin B12 increase during pregnancy [L2064].

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

2-Methyl-3-hydroxy-4,5-dihydroxymethylpyridine | 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine | 3-Hydroxy-4,5-dimethylol-alpha-picoline | 5-Hydroxy-6-methyl-3,4-pyridinedimethanol | Pyridoxine | Pyridoxol | Vitamin B6 | Pyridoxine |

Description

Pyridoxine is the 4-methanol form of vitamin B6, an important water-soluble vitamin that is naturally present in many foods. As its classification as a vitamin implies, Vitamin B6 (and pyridoxine) are essential nutrients required for normal functioning of many biological systems within the body. While many plants and microorganisms are able to synthesize pyridoxine through endogenous biological processes, animals must obtain it through their diet. More specifically, pyridoxine is converted to pyridoxal 5-phosphate in the body, which is an important coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, and aminolevulinic acid. It's important to note that Vitamin B6 is the collective term for a group of three related compounds, pyridoxine, pyridoxal, and pyridoxamine, and their phosphorylated derivatives, pyridoxine 5'-phosphate, pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate. Although all six of these compounds should technically be referred to as vitamin B6, the term vitamin B6 is commonly used interchangeably with just one of them, pyridoxine [A32836]. Vitamin B6, principally in its biologically active coenzyme form pyridoxal 5'-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA) [A32837]. Pyridoxine is used medically for the treatment of vitamin B6 deficiency and for the prophylaxis of isoniazid-induced peripheral neuropathy (due to [DB00951]'s mechanism of action which competitively inhibits the action of pyridoxine in the above-mentioned metabolic functions). It is also used in combination with [DB00366] (as the commercially available product Diclectin) for the treatment of nausea and vomiting in pregnancy.

Indication

Pyridoxine is indicated for the treatment of vitamin B6 deficiency and for the prophylaxis of [DB00951]-induced peripheral neuropathy. It is also approved by Health Canada for the treatment of nausea and vomiting in pregnancy in a combination product with [DB00366] (as the commercially available product Diclectin).

Mechanism of Action

Vitamin B6 is the collective term for a group of three related compounds, pyridoxine (PN), pyridoxal (PL) and pyridoxamine (PM), and their phosphorylated derivatives, pyridoxine 5'-phosphate (PNP), pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP). Although all six of these compounds should technically be referred to as vitamin B6, the term vitamin B6 is commonly used interchangeably with just one of them, pyridoxine. Vitamin B6, principally in its biologically active coenzyme form pyridoxal 5'-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA).

Pharmacodynamics

Vitamin B6 (pyridoxine) is a water-soluble vitamin used in the prophylaxis and treatment of vitamin B6 deficiency and peripheral neuropathy in those receiving isoniazid (isonicotinic acid hydrazide, INH). Vitamin B6 has been found to lower systolic and diastolic blood pressure in a small group of subjects with essential hypertension. Hypertension is another risk factor for atherosclerosis and coronary heart disease. Another study showed pyridoxine hydrochloride to inhibit ADP- or epinephrine-induced platelet aggregation and to lower total cholesterol levels and increase HDL-cholesterol levels, again in a small group of subjects. Vitamin B6, in the form of pyridoxal 5'-phosphate, was found to protect vascular endothelial cells in culture from injury by activated platelets. Endothelial injury and dysfunction are critical initiating events in the pathogenesis of atherosclerosis. Human studies have demonstrated that vitamin B6 deficiency affects cellular and humoral responses of the immune system. Vitamin B6 deficiency results in altered lymphocyte differentiation and maturation, reduced delayed-type hypersensitivity (DTH) responses, impaired antibody production, decreased lymphocyte proliferation and decreased interleukin (IL)-2 production, among other immunologic activities.

Pharmacokinetics

Absorption:

The B vitamins are readily absorbed from the gastrointestinal tract, except in malabsorption syndromes. Pyridoxine is absorbed mainly in the jejunum. The Cmax of pyridoxine is achieved within 5.5 hours.

Distribution:

Pyridoxine main active metabolite, pyridoxal 5’-phosphate, is released into the circulation (accounting for at least 60% of circulating vitamin B6) and is highly protein bound, primarily to albumin.

Metabolism:

Pyridoxine is a prodrug primarily metabolized in the liver. The metabolic scheme for pyridoxine is complex, with formation of primary and secondary metabolites along with interconversion back to pyridoxine. Pyridoxine's major metabolite is 4-pyridoxic acid.

Elimination:

The major metabolite of pyridoxine, 4-pyridoxic acid, is inactive and is excreted in urine

Half-life

The total adult body pool consists of 16 to 25 mg of pyridoxine. Its half-life appears to be 15 to 20 days.

Clearance

Not Available

Toxicity

Oral Rat LD50 = 4 gm/kg. Toxic effects include convulsions, dyspnea, hypermotility, diarrhea, ataxia and muscle weakness.

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

Not Available

Description

Not Available

Indication

Not Available

Mechanism of Action

Not Available

Pharmacodynamics

Not Available

Pharmacokinetics

Absorption:

Not Available

Distribution:

Not Available

Metabolism:

Not Available

Elimination:

Not Available

Half-life

Not Available

Clearance

Not Available

Toxicity

Not Available

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

NEUROBION TABLET (OTC) was registered with Health Science Authority of Singapore by MERCK PTE LTD. It is marketed with the registration number of SIN15098P with effective from 2016-10-13.

This product contains 200mcg of CYANOCOBALAMIN, 200mg of PYRIDOXINE, and 100mg of THIAMINE DISULPHIDE in the form of ORAL TABLET, SUGAR-COATED.

The medicine was manufactured by Merck KGaA in AUSTRIA

It is a an Over-the-counter Medicine which can be freely obtained from any retailer

Anatomical Therapeutic Chemical (ATC) Classification

Products Containing as Single Ingredient

Drug IDTrade NameActive IngredientsForensic ClassRegistrantStatus
1DEXTROMETHORPHAN LINCTUS 15mg/5mlDextromethorphanP OnlyDRUG HOUSES OF AUSTRALIA PTE LTDActive
22ZENMOLIN SYRUP 2mg/5mlSalbutamolP OnlyDRUG HOUSES OF AUSTRALIA PTE LTDActive
41APO-PROPRANOLOL TABLET 40mgPropranololPOMPHARMAFORTE SINGAPORE PTE LTDActive
42APO-DIAZEPAM TABLET 2mgDiazepamPOMPHARMAFORTE SINGAPORE PTE LTDActive
44APO-DIAZEPAM TABLET 5mgDiazepamPOMPHARMAFORTE SINGAPORE PTE LTDActive
45APO-DIAZEPAM TABLET 10mgDiazepamPOMPHARMAFORTE SINGAPORE PTE LTDActive
46APO-PROPRANOLOL TABLET 10mgPropranololPOMPHARMAFORTE SINGAPORE PTE LTDActive
55APO-ISDN TABLET 10mgIsosorbide DinitratePOMPHARMAFORTE SINGAPORE PTE LTDActive
63DIAPO TABLET 10mgDiazepamPOMBEACONS PHARMACEUTICALS PTE LTDActive
64FURMIDE TABLET 40mgFurosemidePOMBEACONS PHARMACEUTICALS PTE LTDActive

Products Containing as Mixture Ingredient

Drug IDTrade NameActive IngredientsForensic ClassRegistrantStatus
4DIPHENHYDRAMINE EXPECTORANTAmmonium Chloride|Diphenhydramine|Sodium CitrateP OnlyDRUG HOUSES OF AUSTRALIA PTE LTDActive
5DIPHENHYDRAMINE EXPECTORANT PAED.Ammonium Chloride|Diphenhydramine|Sodium CitrateP OnlyDRUG HOUSES OF AUSTRALIA PTE LTDActive
400FAKTU SUPPOSITORYCinchocaine|PolicresulenP OnlyTAKEDA PHARMACEUTICALS (ASIA PACIFIC) PTE LTDActive
407TRIMAXAZOLE TABLETSulfamethoxazole|TrimethoprimPOMBEACONS PHARMACEUTICALS PTE LTDActive
435APO-SULFATRIM TABLETSulfamethoxazole|TrimethoprimPOMPHARMAFORTE SINGAPORE PTE LTDActive
508APO-SULFATRIM PEDIATRIC TABLETSulfamethoxazole|TrimethoprimPOMPHARMAFORTE SINGAPORE PTE LTDActive
526B.S. SUSPENSIONSulfamethoxazole|TrimethoprimPOMAPEX PHARMA MARKETING PTE LTDActive
583CO-TRIMEXAZOLE SUSPENSIONSulfamethoxazole|TrimethoprimPOMBEACONS PHARMACEUTICALS PTE LTDActive
676BANEOCIN OINTMENTBacitracin|NeomycinPOMNOVARTIS (SINGAPORE) PTE LTDActive
678BANEOCIN POWDERBacitracin|NeomycinPOMNOVARTIS (SINGAPORE) PTE LTDActive