Chapter 30. Vitamins, iron and treatment of anaemia
LEARNING OBJECTIVES
At the end of this chapter, the reader should be able to:
• give an account of the sources, symptoms of deficiency and preparations for the treatment of the vitamins
• describe the use of antioxidants
• describe the use of iron preparations for treatment of iron deficiency anaemia
• explain the association between anaemia and vitamin B12 deficiency and describe how it is treated
Vitamins
Vitamins are substances which are present in certain foods, but which humans cannot manufacture for themselves. They are necessary for the proper functioning of animal tissues, and a deficiency of vitamins in the diet leads to a number of diseases which are specific for each particular vitamin. Many of the vitamins exert their action by taking part in the complex chemical reactions which occur within the cell.
It is important to realize that provided a sufficiency of vitamins is taken, which should be provided by a good mixed diet, there is no advantage to be gained by taking further large doses of the various vitamins unless there is some form of malabsorption. In fact, the taking of excessive amounts of certain vitamins, for example vitamin A, can even be harmful. At present there is no firm evidence that extra vitamins protect against cancer and heart disease to any appreciable extent, and reports that supplementary vitamins given to children increase their IQ should be treated with scepticism until confirmed.
The vitamins may now be considered in detail:
• vitamin A (retinol) and retinoids
• vitamin B group
• vitamin C (ascorbic acid)
• vitamin D (calciferol)
• vitamin E (tocopherol)
• vitamin K (phytomenadione).
Vitamin A (Retinol)
Occurrence
Retinol is a fat-soluble, oily liquid. It is present in dairy products such as milk, butter and cream and in fish liver oils. Beta-carotene, a substance which is closely allied to retinol and can be converted to retinol by the body, is found in carrots, green vegetables and liver.
Absorption, function and deficiency
The absorption of retinol is helped by the presence of fat and bile salts in the intestine. Retinol is concerned with maintaining the health of the epithelium. Deficiency leads to keratinization of the epithelium of the nose and respiratory passage and to changes in the conjunctiva and in the cornea that may lead to blindness. Retinol is also concerned with the mechanism of dark adaptation by the retina and deficiency leads to night blindness.
Therapeutic use
Retinol should be given in cases of deficiency causing night blindness or epithelial changes. The minimum human requirements in the adult are 2250 IU (international units) daily. The therapeutic dose is 50 000 IU.
Toxicity
Overdosage with retinol can produce liver damage, headache and vomiting. Fatalities have been reported. Pregnant and breastfeeding women are advised to avoid vitamin A supplements or liver products as there is some evidence that excessive intake is associated with fetal defects.
Retinoids
These substances are related to vitamin A, but are used for their effect on the skin.
Therapeutic use of retinoids
Safety note
Retinoids have severe potential toxicity and teratogenicity and should be used under expert supervision.
Retinoids are used mainly in the treatment of psoriasis and acne. Calcitriol is an active form of vitamin A. Acitretin causes desquamation of the skin (the process in which the outer layer of the epidermis is removed by scaling). Its main indication is for psoriasis, although it is also prescribed for other keratinization disorders such as ichthyosis and Darier’s disease (keratosis follicularis). Isotretinoin can be applied locally and taken systemically in the treatment of acne, where it reduces the secretion of sebum. Tazarotene is an odourless retinoid that is effective for psoriasis. Tretinoin is the acid form of vitamin A and is used topically for the treatment of acne.
Adverse effects and precautions
Topical application
Both isotretinoin and tretinoin may cause peeling of the skin and reddening when first used, but this effect usually disappears after a period of time. All retinoids for topical use should be used sparingly and applied thinly to the skin. They should not be smeared over large areas of skin, especially if the acne is severe. Contact with broken or sunburned skin, mucous membranes, mouth, nose and eyes should be avoided, and patients who apply these should protect their skin from direct sunlight and not use ultraviolet (UV) lamps.
Oral use
Patients taking retinoids orally should have regular tests of liver function and blood lipid concentrations. Patients taking retinoids orally may experience effects on epithelial tissues, such as sticky palms, cracked and dry lips, paronychia (whitlows), which is a painful swelling of the nail folds, and hair thinning. These are reversible effects.
Safety note
Contraindications
Nursing point
Safety note
Acute paronychia is associated with Staphylococcus aureus, and chronic paronychia is associated with Candida albicans, and with those whose work entails hands being continually wet (e.g. cleaners, hairdressers). It is always important to dry hands thoroughly after contact with water.
Contraindications
Retinoids alter cell division and are teratogenic (cause fetal malformations). They must not be used in pregnancy or during breastfeeding, especially when for oral use. The danger of possible teratogenicity can persist for years after stopping oral treatment with retinoids. With acitretin, for example, whose main indication is for psoriasis, it is recommended that patients with childbearing potential should cease taking the drug for at least 2 years before a planned pregnancy.
Nursing point
Nurses who apply these preparations topically should always wear gloves (see also p. 208).
Vitamin B group
The vitamin B group comprises:
• Thiamine (vitamin B 1)
• riboflavin (vitamin B 2)
• nicotinic acid (niacin, nicotinamide, niacinamide)
• pyridoxine (vitamin B 6)
• cyanacobalamin (vitamin B 12).
Thiamine (vitamin B 1)
Occurrence
Vitamin B 1 is a white crystalline solid, soluble in water. It is obtained from wheat germ, yeast, egg yolk, liver and some vegetables.
Function and deficiency
Vitamin B 1 is essential for certain stages of carbohydrate metabolism. Deficiency of this vitamin leads to a nervous system disorder known as beriberi. This deficiency may not only result from an inadequate intake of vitamin B 1 but may also occur in disturbances of metabolism in which requirements of vitamin B 1 are higher than normal, a good example being chronic alcoholism. Beriberi is characterized by heart failure and polyneuritis.
Therapeutic use
Beriberi responds rapidly to vitamin B 1. Severe cases will require up to 100 mg daily by intramuscular injection; in milder cases, oral administration is satisfactory. Vitamin B 1 is also used in high doses in the polyneuritis of chronic alcoholism and in Korsakov’s psychosis and Wernicke’s encephalopathy, which are also usually due to excess alcohol. The minimum human requirement for adults is 2 mg daily. The normal therapeutic dose is 50 mg orally or intravenously daily.
Adverse effects
Patients given parenteral thiamine should be observed afterwards in case of an anaphylactic reaction.
Vitamin B 2 (riboflavin)
Occurrence
This vitamin is found in high levels in fish, egg yolks, cheese, meat, milk, poultry and whole grains.
Function and deficiency
Vitamin B 2 is necessary for antibody production, red cell formation, cell respiration and growth. Deficiency in humans causes several symptoms, including cracking and fissures at the corner of the mouth and a sore tongue and skin lesions. The syndrome is called ariboflavinosis.
Therapeutic use
Vitamin B 2 may be given in doses of 2 mg daily. Some sources recommend an increased intake of this vitamin when taking oral contraceptives or during periods of strenuous exercise. Vitamin B 2 is destroyed by light, alcohol and antibiotics.
Nicotinic acid
Nicotinic acid is also called niacin. Some sources refer to it as vitamin B 3.
Occurrence
Nicotinic acid is found in high concentrations in brewer’s yeast, dairy products and beef liver.
Function
Nicotinic acid is a derivative of pyridine, from which the pyridine nucleotides, building blocks of DNA and RNA, are derived. Nicotinamide is the amide of nicotinic acid and is a component of the ubiquitous co-enzyme NAD (nicotinamide adenine dinucleotide). It is therefore vital for the proper functioning of a large number of enzymes in the body. It is important in the production of hydrochloric acid in the stomach and is involved in the normal secretion of gastric and bile fluids. It has been claimed to lower cholesterol and aid circulation. It is needed for proper synthesis of the sex hormones. It is important for normal operation of the nervous system.
Deficiency
Deficiency of nicotinamide leads to a disorder known as pellagra, which may occur in alcoholism and renal failure as well as with deficient diets. This disease is characterized by the ‘3Ds’ – namely, diarrhoea, dermatitis and dementia.
Therapeutic use
Nicotinamide is available both in a 50 mg tablet and in cream form. The cream is used topically in the treatment of acne vulgaris and the tablets are used to treat nicotinamide deficiency.
Adverse effects
It is worthwhile remembering that nicotinamide is also a vasodilator. If it is taken in large doses, flushing and tingling of the face may occur. High doses can cause liver damage if taken for prolonged periods. Pregnant women and those suffering from diabetes, liver disease, gout, glaucoma or peptic ulcers should use nicotinic acid with caution and in any event should take medical advice before taking it.
Vitamin B 6 (pyridoxine)
Occurrence
Pyridoxine occurs in all foods. High levels are found in brewer’s yeast, walnuts, carrots, poultry, eggs, fish, meat, peas (not well cooked), and wheat germ and sunflower seeds.
Function
Pyridoxine is involved in very many metabolic processes. It is required for normal functioning of the nervous system, including the brain. It is involved in red blood cell formation and for that of DNA and RNA. It is important in immune function and is part of the body’s mechanisms to prevent atherosclerosis. It is required for healthy heart function since it blocks the formation of homocysteine, a toxic chemical that promotes the deposition of cholesterol around heart muscle.
Deficiency
Deficiency of pyridoxine causes:
• dry and flaking skin
• nausea and vomiting
• headache
• sore tongue
• CNS symptoms, e.g. convulsions, difficulty with concentration, weak memory.
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