Vitamins - Pharmacology

Vitamins Pharmacology

Vitamins are organic chemicals that are required for metabolic activities necessary for tissue growth and healing. Under normal conditions, only a small amount of vitaminswhich are provided by eating a well-balanced dietare necessary.

However, larger amounts of vitamins should be taken if the patient is pregnant, undergoing rapid growth or has a debilitating illness. Likewise, patients who do not have a well-balanced diet (such as the elderly, alcoholics, children, and those who go on fad diets) might also develop a vitamin deficiency. That would require the patient to take vitamin supplements to assure there are sufficient vitamins to support his or her metabolism.

Expect to provide vitamin supplements for patients who have:

  • Conditions that inhibit absorption of food.
  • Diarrhea.
  • Infection and fever.
  • Inflammatory diseases.
  • Cancer.
  • Inability to use vitamins.
  • Undergoing hemodialysis.
  • Hyperthyroidism.
  • GI surgery.
  • Fad diets.
  • Are pregnant.
  • Growing children.

WELL-BALANCED DIET

Many patients realize the importance of having a well-balanced diet. Few however, know what constitutes a well-balanced diet. Patients can use the U.S. Department of Agriculture’s (USDA) definition of a well-balanced diet as a guideline.

The USDA uses a food pyramid to illustrate the mixture of food groups that are necessary for us to receive the proper amount of vitamins and minerals for a healthy life. Recently the USDA revised its longstanding food pyramid to reflect the individual needs of people of a specific age, sex, and activity group. The previous food pyramid placed everyone in the same group, which is not realistic. The revised food pyramid is organized into five color-coded groups, each with a general recommendation.

  • Grains. Three ounces of whole grain bread, rice, cereal, crackers, or pasta every day (orange).
  • Vegetables. Eat more dark green vegetables, orange vegetables, beans and peas (green).
  • Fruits. Fresh frozen, dry, or canned fruit. Go easy on fruit juices (red).
  • Milk. Calcium-rich foods. Choose lactose free products (blue).
  • Meat and beans. Low-fat and lean meats and poultry. Bake it, broil it, grill it. More fish, beans, peas, nuts and seeds (purple).

However, the USDA has a web site (http://www.mypyramid.gov/pyramid/ index.html) that will calculate the desired portions for each group based on a person’s age, sex, and the amount of exercise the person performs daily. In addition to the USDA, the National Academy of Sciences Food and Nutrition Board (http://www.iom.edu) publishes the U.S. Recommended Dietary Allowance (RDA) for daily dose requirements of each vitamin (recommended dietary allowances).

RDA (recommended dietary allowances).

Table : RDA (recommended dietary allowances).

TYPES OF VITAMINS

There are two groups of vitamins. These are fat-soluble vitamins and watersoluble vitamins.

Fat-soluble vitamins

Fat-soluble vitamins are absorbed by the intestinal tract following the same metabolism as used with fat. Any condition that interferes with the absorption of fats will also interfere with the absorption of fat-soluble vitamins. Fat-soluble vitamins are stored in the liver, fatty tissues and muscle and remain in the body longer than water-soluble vitamins. Fat-soluble vitamins are excreted slowly in urine. Hint to remember: ADEK = addicted to fat are fat soluble vitamins. The following are fat-soluble vitamins.

Vitamin A

Vitamin A (Acon, Aquasol) helps to maintain epithelial tissue, eyes, hair and bone growth. It is also used for treatment of skin disorders such as acne. Vitamin A has a toxic effect if taken in excess. For example, birth defects can occur if the patient takes greater than 6000 international units (IU) during pregnancy. It is important to keep in mind that Vitamin A is stored in the liver for up to two years, which can result in inadvertent toxicity if the patient is administered large doses of Vitamin A.

Vitamin D

Vitamin D, absorbed in the small intestine with the assistance of bile salts, is necessary for the intestines to absorb calcium. Vitamin D plays a major role in

Vitamin A

Vitamin A

Vitamin D

Vitamin D

Vitamin E

regulating the metabolism of calcium and phosphorus. There are two forms of Vitamin D: D2, called ergocalciferol; and D3, called cholecalciferol. D2 is a synthetic fortified form of Vitamin D. D3 is the natural form of Vitamin D that is produced in the skin by ultraviolet sunlight. Once absorbed, Vitamin D is converted into calcifediol in the liver and then converted to an activated form of calcifediol in the kidneys. The active form is a hormone that combines with parathyroid hormone (PTH) and calcitonin to regulate calcium and phosphorus metabolism in the body and stimulate the reabsorption of calcium and phosphorus by bone. When serum levels of calcium are low, more Vitamin D is used to create the active form of calcifediol. Low serum levels of calcium cause a decrease in the creation of the active form of calcifediol. Excess Vitamin D is then excreted in bile and a small amount is excreted in urine.

Vitamin E

Vitamin E

Vitamin E protects the heart and arteries and cellular components from being oxidized and prevents red blood cells from hemolysis (rupture). If there is a sufficient balance of salts, pancreatic secretion, and fat, Vitamin E is absorbed from the GI tract and stored in all tissues, especially in the liver, muscle, and fatty tissues. Seventy-five percent of excess Vitamin E is excreted in the bile and the remainder is excreted in urine.

Vitamin K

Vitamin K comes from dietary sources such as leafy green vegetables, liver, cheese, and egg yolk and is synthesized by intestinal flora. Vitamin K is required to synthesize prothrombin and clotting factors VII, IX, and X and is an antidote for oral overdose of the anticoagulant Coumadin (Warfarin). There are four forms of Vitamin K: K1 (phytonadione), which is the active form; K2 (menaquinone), which is synthesized by intestinal flora, but not commercially available; K3 (menadione) and K4 (menadiol), both of which are produced synthetically. K1 and K2 are absorbed in the presence of bile salts. K3 and K4 are absorbed without bile salts. Vitamin K1 prevents hemorrhage and is available as Mephyton, AquaMEPHYTON, and Konakion. Vitamin K4 is available as Synkayvite. Vitamin K is absorbed in the intestines and is stored in the liver and in other tissues.

Water-soluble vitamins

Water-soluble vitamins are also known as the B Complex because it was originally considered as one vitamin. It was later discovered that these are separate vitamins. The following are water-soluble vitamins.

TABLE

Vitamin K

Vitamin K

Vitamin C

Vitamin C may be found in citrus fruits, tomatoes, leafy green vegetables, and potatoes and used to metabolize carbohydrates and used for synthesis of protein, lipids, and collagen. Vitamin C is also required for capillary endothelium and repair of tissues. Vitamin C aids in the absorption of iron and the metabolism of folic acid. Unlike fat-soluble vitamins, vitamin C is not stored in the body and is excreted in urine. However, high serum levels of vitamin C can result from excessive doses and be excreted without any change. Vitamin C is commercially available as Ascorbicap, Cecon, Cevalin, Solucap C.

TABLE

Vitamin C

Vitamin C

Vitamin B Complex

Vitamin B complex consists of four vitamins. These are B1 (thiamine), B2 (riboflavin), B3 (niacin), and B6 (pyridoxine). B1 is used to treat peripheral neuritis from alcoholism or beriberi. B2 is used to manage dermatologic problems, such as scaly dermatitis, cracked corners of the mouth, inflammation of the skin and tongue. B3 is given in large doses to alleviate pellagra (dietary deficiency of niacin) and hyperlipidemia and may cause GI irritation and vasodilatation resulting in a flushing sensation. B6 is given to correct B6 deficiency and helps alleviate symptoms of neuritis causes by isoniazid (INH) therapy for tuberculosis.

TABLE

Vitamin B Complex

Vitamin B Complex

Folic Acid (Folate, Vitamin B9 )

Folic acid is essential for body growth and is needed to synthesize DNA. Folic acid is found in leafy green vegetables, yellow fruits and vegetables, yeast, and meat and is absorbed in the small intestine. The active form of folic acidcalled folatecirculates to all tissues in the body. A third of folate is stored in the liver and the remainder is stored in other tissues. Most folic acid is excreted in bile and a small amount in urine. Chronic alcoholism, poor nutrition, pregnancy, and diseases that disrupts absorption by the small intestine can lead to an inadequate amount of folic acid. This can disrupt cellular division. A patient with low folic acid has nausea and diarrhea and is anorexic, fatigued, and has stomatitis, alopecia, and blood dyscrasias (megaloblastic anemia, leucopenia, and thrombocytopenia). Symptoms usually do not appear for 2 to 4 months after folic acid storage is depleted.

Folic Acid (Folate, Vitamin B9 )

TABLEFolic acid

Vitamin B12

Vitamin B12 may be found in liver, kidney, fish, and fortified milk and helps convert folic acid into its active form. Vitamin B12 is essential to synthesize DNA and promotes cellular division and is required for hematopoiesis (development of red blood cells in bone marrow) and to maintain the integrity of the nervous system. Vitamin B12 is absorbed in the intestine with the aid of an intrinsic factor produced by gastric parietal cells. Once absorbed, vitamin B12 binds to thetranscobalamin II protein and is then transferred to tissues. Vitamin B12 is stored in the liver for up to three years during which time it is slowly excreted in urine. Vitamin B12 deficiency is common in patients who are strict vegetarians and in patients who have malaborption syndromes (cancer, celiac disease), gastrectomy, Crohn’s disease, and liver and kidney diseases.

Vitamin B12

TABLE :Vitamin B12


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