Source: Υπουργείο Υγείας (CY) Revision Year: 2020 Publisher: BIAL – Portela & Cª, S.A., À Av. da Siderurgia Nacional, 4745 457 S. Mamede do Coronado, Portugal
Pharmacotherapeutic group: 11.3.1.3 Association of vitamins
ATC code: A11BA
Vitamins are a group of substances with several chemical compositions which may be defined as organic substances that should be supplied in small amounts in diet, to the synthesis, by tissues, of co-factors which are essential to several metabolic reactions. Vitamins may be used in Medicine by two different purposes:
The second type of use may be prophylactic, or, if the multivitamin deficiency already exists, with therapeutic purposes.
VICOMBIL is a multivitamin formulation to be used as supplement when an inadequate intake of vitamins is evident. Its balanced composition according to the daily vitamin requirements as established by the Dietary Allowances Committee of the Food and Nutrition Board of the USA (RDA). The use of vitamin supplements is clinically recommended in several circumstances where vitamin deficiencies may take place, being this practice universally accepted.
Retinol plays an important role on the retina function. It is necessary for growth and differentiation of the epithelial tissue, bone growth and embryonal development. The recommended dose as supplement is of approximately 5.000 IU (corresponding to Retinol 1.000 Eq). Daily intake of this dose does not develop vitamin A accumulation or Risk of hypervitaminosis.
Thiamine Hydrochloride acts on the body as thiamine pyrophosphate. This last has functions on the carbohydrate metabolism, as coenzyme in carbohydrate, in the decarboxylation of alfa-ketoglutaric acids and in the utilization of pentose in the hexose monophosphate shunt. It appears to act as modulator of cholinergic transmission.
Thiamine requirements are related with the metabolic rate, being higher when the carbohydrates are the main energy source. Daily supplemental intake should not be less than 1.5 mg, but in several circumstances, it is necessary to increase the amount of this vitamin. Thiamine deficiency may occur in association with an apparently adequate dietary intake, since this vitamin is not stored in the human body in large amounts.
Riboflavine has its functions in the organism as one of two coenzymes. This vitamin plays a fundamental role in the metabolism, as coenzyme in a wide range of respiratory flavoproteins, some of which containing metals. The daily supplementation should not be less than 1.6 mg.
Pyridoxine hydrochloride is converted in the human body to three active forms of the vitamin: pyridoxine, pyridoxal and pyridoxamine. This vitamin plays an important role in the metabolism, as coenzyme in a wide variety of reactions in intermediary metabolism of amino acids, including decarboxylation and transamination, as well as to the enzymatic metabolic steps of tryptophan and hydroxy-amino acids. It is recommended a supplemental intake not less than 2.2 mg.
Cyanocobalamin is converted to two active coenzymes: methylcobalamin and deoxyadenosylcobalamin. These active coenzymes are essential to growth and cell multiplication. Deoxyadenosilcobalamin is a co-factor to the mitochondrial mutase enzyme that catalyses L-methyl-malonil-Coa isomerization to succinyl CoA, an important reaction both for carbohydrates metabolism and lipids. Methylcobalamin supports the methionine synthetase reaction, which is essential to the normal folate metabolism. Interaction folate-cobalamin is essential to the normal synthesis of purines and pyrimidines and therefore to ADN. It is also responsible for the maintenance of a certain amount of methylation reactions. When vitamin B1 concentrations decrease, folate remains imprisoned as methyl-tetrafolate, leading to a functional deficiency of other vital and intracellular forms of folic acid.
An additional dose of 1mcg of B12 is commonly adequate. When higher doses are needed, a preparation containing exclusively B12 should be administered. IM route should be used in case of pernicious anaemia, a disease for which a multivitamin preparation such as VICOMBIL is not adequate.
Ascorbic acid (Vitamin C) enters in various biochemical reactions, most of them involving oxidation. It is a strong reducing agent and participates in oxidation-reduction cellular reactions. It appears to be particularly important to bone, teeth and collagen formation. In the adrenal cortex there are high amounts of vitamin C from where it can be released by ACTH intervention. The most important sources of vitamin C are fruits and fresh green vegetables. It is usually recommended a daily dose not below 65 mg.
Ergocalciferol (vitamin D2) is a vitamin D stable form which is active when it is administered when vitamin D is mandatory. Ergocaciferol is transferred to the liver where it is converted to calcifediol, which is then transferred to the kidney and converted to calcitriol, the most active form of vitamin D. However, in medicinal formulations, ergocalciferol is the choice because in opposition to calcitriol, it is chemically stable. Vitamin D is a regulator of calcium homeostasis. The two most important mechanisms through which vitamin D acts to maintain normal serum concentrations of calcium and phosphate in plasma, are the absorption facilitation of both at the intestinal level and promotion of its mobilization through the bone. Also, vitamin D2 acts upon the kidney leading to a retention of calcium and phosphorous due to tubular resorption.
Doses under 5.000IU (12.5 mcg) or over 50.000 IU should not be administered, according to clinical indication (prophylaxis or treatment).
Nicotinamide (vitamin PP) occurs in the liver, meat and yeasts and may be synthesised by intestinal bacteria. It is a component of coenzymes and nucleotides and is present in live cells.
When associated to specific proteins of oxidation-reduction systems, these coenzymes, accept hydrogen atoms which further transfer to other enzymes. This vitamin is, therefore, necessary to several reactions that are essential to cells life.
Folic acid is a very important enzyme to the cellular metabolism. After absorption, the pteroylglutamic acid is rapidly reduced in positions 5,6, 7 and 8, giving birth to tetra-hydrofolic acid which acts as a receptor to a set of units of one-carbon atom. They link to positions 5 or 10 originating active forms of coenzyme, each of them having a specific metabolic role.
The active form of calcium pantothenate is the coenzyme A. It serves as co-factor in several reactions catalyzed enzymatically and involving acetylic groups transfer. These reactions are important in oxidative metabolism of carbohydrates, in glycogenesis, in the synthesis and degradation of fat acids, in the synthesis of sterols, of steroid hormones and porphyrines.
Calcium pantothenate may be synthesized by intestinal bacteria.
All vitamins in VICOMBIL are well absorbed by digestive tract. Once absorbed they are more or less stored and metabolized. However vitamin B12 is rapidly absorbed if there does not exist deficiency of the intrinsic factor or ileum disease.
Vitamin A is stored in the liver in several stores, from which other organs are supplied. Vitamin A concentration in the liver is about 100 mcg/g. Retinol is partially conjugated, forming a beta-glucoronid conjugate that enters in the entero-hepatic circulation and is oxidised to retinal and retinoic acid.
Vitamin B1, which has a maximum absorption limit by the digestive tract of 8-15mg/day, is completely degradated in tissues if the administered amount does not exceed 1 mg/day. When that amount exceeds 1 mg, organic stores are saturated. The remaining appears in urine as unchanged thiamine or pyrimidine. Only 9% of Vitamin B2 appears in urine when the intake is near the daily requirements. The more the intake exceeds these requirements, the more of unchanged Vitamin B2 is excreted.
Also, nicotinamide is distributed to tissues. When it is administered at therapeutic doses, only small amounts appear in urine. If those doses increase larger amounts appear progressively in urine.
As with other vitamins, Vitamin B6 is well absorbed orally, and is excreted, mainly as 4-pyridoxic acid.
Calcium pantothenate is well absorbed and is excreted unchanged. Vitamin B12 deficiencies reflect, in general, a reduction on the capacity of absorption of the gastrointestinal mucosa. Once absorbed Vitamin B12 binds to transcobalamin II, a plasmatic globulin that transport it to the tissues. The liver is the major store. More than 90% of Vitamin B12 in the body (1-10 mg) is in that organ.
When folic acid is absorbed, it is rapidly converted to CH3 H4 Pteglu1. Folates are then stored in the cells as glutamates.
After Vitamin C is absorbed, it is distributed to every cell in the body. A daily dose of 5-10 mg leads to an organic store of 6000-1.000 mg ascorbic acid. If daily intake reaches 200 mg, the stores increase to 2.500 mg, with plasmatic levels of 2 mg/dl. Since the renal threshold is 1.5 mg/dl, the kidney excretes the amounts exceeding 100 mg intake.
Vitamin E enters in the blood flow helped by the lymph. It is distributed to all tissues. Seventy-eight per cent of vitamin E is excreted in the liver.
After Vitamin D absorption, it circulates in the blood bound to a protein. The main excretion route of Vitamin D is the bile.
The safety of use of the different vitamins in VICOMBIL is well established: The hydrosoluble ones are practically nontoxic, except for the cases of susceptibility to vitamins B1 and B2 and the possibility of folic acid, when administered alone in case of pernicious anaemia, to hide a haematological condition and allow the development of haematological complications.
As for the liposoluble vitamins, especially A and D, they may, if high doses are administered, be toxic to Man, leading to hypervitaminosis, especially in children. Therefore, in some adults taking doses higher than 25.000/day of vitamin A, that is, 5 times more the daily recommended doses, some hypervitaminosis diagnosis occurred.
Also, the administration of ergocalciferol, acute or chronic (1.25 to 2.5 mg/day) led to hypervitaminosis D, manifested by hipercalcemia.
For prophylactic purposes the multivitaminic preparation may contain 50 to 100% of RDA, and for therapeutic purposes 3-5 times the RDA, except for vitamin D and folic acid which should not exceed the RDA.
Both the quantity per dose unit and the posology established for VICOMBIL meet these exact requirements.
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