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Australian Journal of Pharmacy : November 2006
pharmacy ed counselling casebook • approved CPE Medication implementations: Excessive folic acid is not toxic, however, it may worsen the symptoms of a coexisting vitamin B12 deficiency and should never be taken to treat anaemia without a full medical investigation of the cause of the anaemia.3–6 Folate supplementation may be required in patients taking phenytoin or long-term trimethoprim.19 In patients taking methotrexate, folic acid supplementation decreases the risk of adverse effects such as nausea and mouth ulcers and is given at a dose of around 10mg weekly in single or split doses, but gen- erally not on the day that methotrexate is taken.22 Pyridoxine (Vitamin B6) has a role in the activity of many enzymes required for production of erythrocytes and antibodies, for healthy skin and healthy digestion. Pyridoxine deficiency is rare but, when it occurs, symptoms are weakness, irritability, nervousness, depression, skin disorders, inflammation of the mouth and tongue, and cracked lips. In adults, it may cause anaemia and convulsions may occur in infants. Food sources include liver, whole grain cereals, meat, fish, peanuts, bananas, walnuts, avocados, potatoes and beans. Supranutritional doses: Daily doses of exceeding 200mg taken over a prolonged period may damage the nervous system, result- ing in unsteadiness, numbness, and awkwardness of the hands. Severe peripheral neuropathies have been reported.3–6,10 A systematic review of many trials on the effectiveness of pyri- doxine in the management of premenstrual syndrome found that conclusions were limited by the poor quality of most of the trials included. However, the results do suggest that doses of vitamin B6 up to 100mg/day may to be of some benefit in treating pre- menstrual symptoms and premenstrual depression.23 Medication implementations: Pyridoxine supplementation may be required for patients taking hydralzine, isoniazid, penicilli- namine.19,23 Pyidoxine may reduce phenytoin levels.19 Cyanocobalamin (B12) has a role in activities of several enzymes. It is essential for the manufacture of genetic material of cells and the formation of erythrocytes by bone marrow. Deficiency: Vitamin B12 deficiency usually develops over months or years—the liver can store up to a six-year supply— leading to pernicious anaemia, and the mouth and tongue often become sore. Deficiency also affects the brain and spinal cord, leading to numbness and tingling of the limbs, memory loss, and depression.3–6 Treatment is the administration of cyanocobalamin 1,000mcg/mL (Cytamen) once a month or 100mcg tablets (Blackmores) twice daily or Hydroxycobalamin (Neo-Cytamen) 1,000iu/mL) every two to three months.24 Food sources include liver (richest source), kidney, sardines, oysters, fish, lean rabbit, other meats, eggs, cheese and milk. Medication implementations: B12 supplementation may be required in patients taking carbamazepine, metformin, H2 recep- tor antagonists, and proton pump inhibitors.10,19 70 ? THE AUSTRALIAN JOURNAL OF PHARMACY VOL.87 NOVEMBER 2006 Vitamin C (ascorbic acid) plays an essential role in the activi- ties of several enzymes. It is vital for the growth and maintenance of healthy bones, teeth, gums, ligaments, and blood vessels, and is an important component of all body organs. It is important for the manufacture of certain neurotransmitters, adrenal hor- mones, is essential in the utilisation of folic acid and absorption of iron, is necessary for normal immune responses to infection and for wound healing. Mild deficiency may cause weakness, aches and pains, swollen gums, and nosebleeds. Severe deficiency results in scurvy, the symptoms of which include inflamed, bleeding gums, excessive bruising, and internal bleeding. In adults, bones fracture easily and teeth become loose. In children, there is abnormal bone and tooth development. Wounds fail to heal and become infected. Deficiency often leads to anaemia. Untreated scurvy may cause fits, coma, and death. Food sources of vitamin C include blackcurrants, guavas, rose- hip syrup, green peppers, oranges, other citrus fruit, strawber- ries, cauliflower, broccoli, sprouts, cabbage, watercress, pota- toes.3–6 The risk of harmful effects is low, as excess vitamin C is excreted in the urine. However, doses of more than 1g daily may cause diarrhoea, nausea, and stomach cramps. Vitamin C, like vitamin E and ß-carotene, is a biochemical antioxidant and hence many claims have been made as to its and their benefits in prevention of heart disease and cancer with little evidence to support these claims (see vitamin E). Linus Pauling was largely responsible for the widespread misbelief that high doses of vita- min C are effective against colds and other illnesses.25 A 2005 meta-analysis of a large number of trials found that vitamin Csupplementation failed to reduce the incidence of colds in the normal population. Evidence shows, however, that it could be justified in persons exposed to brief periods of severe physical exercise and/or cold environments. Also, the consistent and sta- tistically significant small benefits on duration and severity for those using regular vitamin C prophylaxis indicates that vitamin C plays some role in respiratory defence mechanisms. The trials in which vitamin C was introduced at the onset of colds as ther- apy did not show any benefit in doses up to 4 grams daily. The authors recommend that routine mega-dose prophylaxis with vitamin C is not rationally justified for community use.26 Multivitamins: The sensible purpose of multivitamin prepa- rations might be considered as an insurance policy for people whose diet may be restricted or unbalanced but neither they nor the sellers of the preparations is sure which vitamin is lacking. There is a case for multivitamin supplements for people with a low kilojoule intake because of poor appetite or a weight-reduc- ing diet or frailty, also for food faddists, the emotionally disturbed and socially disadvantaged people.27 The dose of each vitamin should be near the recommended nutritional requirements. References available on request