Vitamin B is composed of widely differing substances which are, for convenience, classed as ‘vitamin B complex’. Thiamine (vitamin B1 ) is used orally for deficiency due to to inadequate dietary intake. Severe deficiency may result in ‘beri-beri’. Chronic dry ‘beri-beri’ is characterized by peripheral neuropathy, muscle wasting and weakness, and paralysis; wet ‘beri-beri’ is characterized by cardiac failure and oedema. Wernicke-Korsakoff syndrome (demyelination of the CNS) may develop in severe deficiency. Thiamine is given by intravenous injection in doses of up to 300 mg daily (parenteral preparations may contain several B group vitamins) as initial treatment in severe deficiency states. Potentially severe allergic reactions may occur after parenteral administration. Facilities for resuscitation should be immediately available. Riboflavin (vitamin B2 ) deficiency may result from reduced dietary intake or reduced absorption due to liver disease, alcoholism, chronic infection or probenecid therapy. It may also occur in association with other deficiency states such as pellagra. Pyridoxine (vitamin B6 ) deficiency is rare as the vitamin is widely distributed in foods, but deficiency may occur during isoniazid therapy and is characterized by peripheral neuritis. High doses are given in some metabolic disorders, such as hyperoxaluria and it is also used in sideroblastic anaemia. Nicotinic acid inhibits the synthesis of cholesterol and triglyceride and is used in some hyperlipidaemias. Nicotinic acid and nicotinamide are used to prevent and treat nicotinic acid deficiency (pellagra). Nicotinamide is generally preferred as it does not cause vasodilation. Hydroxocobalamin is the form of vitamin B12 used to treat vitamin B12 deficiency due to dietary deficiency or malabsorption (see section 10.1).
Tags: cardiac failure, group vitamins, nicotinic acid, pellagra, vitamin b, vitamin b1, vitamin b12 deficiency, vitamin b2 deficiency, vitamin b6 deficiency
