There can be variation in the licensing of
different medicines containing the same drug.
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Vitamin deficiency
Vitamins
Overview
Vitamins are used for the prevention and treatment of
specific deficiency states or where the diet is known to be
inadequate; they may be prescribed in the NHS to prevent or
treat deficiency but not as dietary supplements.
Their use as general ‘pick-me-ups’ is of unproven value
and, in the case of preparations containing vitamin A or D,
may actually be harmful if patients take more than the
prescribed dose. The ‘fad’ for mega-vitamin therapy with
water-soluble vitamins, such as ascorbic acid p. 1143 and
pyridoxine hydrochloride p. 1141, is unscientific and can be
harmful.
Dietary reference values for vitamins are available in the
Department of Health publication:
Dietary Reference Values for Food Energy and Nutrients
for the United Kingdom: Report of the Panel on Dietary
Reference Values of the Committee on Medical Aspects of
Food Policy. Report on Health and Social Subjects 41. London:
HMSO, 1991.
Dental patients
It is unjustifiable to treat stomatitis or glossitis with
mixtures of vitamin preparations; this delays diagnosis and
correct treatment.
Most patients who develop a nutritional deficiency despite
an adequate intake of vitamins have malabsorption and if
this is suspected the patient should be referred to a medical
practitioner.
Vitamin A
Deficiency of vitamin A p. 1140 (retinol) is associated with
ocular defects (particularly xerophthalmia) and an increased
susceptibility to infections, but deficiency is rare in the UK
(even in disorders of fat absorption).
Vitamin B group
Deficiency of the B vitamins, other than vitamin B12, is rare
in the UK and is usually treated by preparations containing
thiamine p. 1141 (B1), riboflavin (B2), and nicotinamide
p. 1339, which is used in preference to nicotinic acid p. 213,
as it does not cause vasodilatation. Other members (or
substances traditionally classified as members) of the
vitamin B complex such as aminobenzoic acid, biotin,
choline, inositol nicotinate p. 247, and pantothenic acid or
panthenol may be included in vitamin B preparations but
there is no evidence of their value.
The severe deficiency states Wernicke’s encephalopathy
and Korsakoff’s psychosis, especially as seen in chronic
alcoholism, are best treated initially by the parenteral
administration of B vitamins (Pabrinex ®), followed by oral
administration of thiamine in the longer term. Anaphylaxis
has been reported with parenteral B vitamins.
As with other vitamins of the B group, pyridoxine
hydrochloride (B6) deficiency is rare, but it may occur during
isoniazid p. 621 therapy or penicillamine p. 1158 treatment
Blood and nutrition
in Wilson’s disease and is characterised by peripheral
neuritis. High doses of pyridoxine hydrochloride are given in
some metabolic disorders, such as hyperoxaluria, and it is
also used in sideroblastic anaemia. There is evidence to
suggest that pyridoxine hydrochloride may provide some
benefit in premenstrual syndrome. It has been tried for a
wide variety of other disorders, but there is little sound
evidence to support the claims of efficacy.
Nicotinic acid inhibits the synthesis of cholesterol and
triglyceride. Folic acid p. 1084 and vitamin B12 are used in the
treatment of megaloblastic anaemia. Folinic acid p. 992
(available as calcium folinate) is used in association with
cytotoxic therapy.
Vitamin C
Vitamin C (ascorbic acid) therapy is essential in scurvy, but
less florid manifestations of vitamin C deficiency are
commonly found, especially in the elderly.
Severe scurvy causes gingival swelling and bleeding
margins as well as petechiae on the skin. This is, however,
exceedingly rare and a patient with these signs is more likely
to have leukaemia. Investigation should not be delayed by a
trial period of vitamin treatment.
Claims that vitamin C ameliorates colds or promotes
wound healing have not been proven.
Vitamin D
The term Vitamin D is used for a range of compounds which
possess the property of preventing or curing rickets. They
include ergocalciferol p. 1148 (calciferol, vitamin D2),
colecalciferol p. 1145 (vitamin D3), dihydrotachysterol
p. 1147, alfacalcidol p. 1144 (1a-hydroxycholecalciferol), and
calcitriol p. 1144 (1,25-dihydroxycholecalciferol).
Simple vitamin D deficiency can be prevented by taking an
oral supplement of ergocalciferol (calciferol, vitamin D2) or
colecalciferol (vitamin D3) daily. Vitamin D deficiency can
occur in people whose exposure to sunlight is limited and in
those whose diet is deficient in vitamin D. In these
individuals, ergocalciferol or colecalciferol daily by mouth
may be given to treat vitamin D deficiency; higher doses may
be necessary for severe deficiency. Patients who do not
respond should be referred to a specialist.
Preparations containing colecalciferol with calcium
carbonate p. 1146 are available for the management of
combined calcium and vitamin D deficiency, or for those at
high risk of deficiency.
Vitamin D deficiency caused by intestinal malabsorption or
chronic liver disease usually requires vitamin D in
pharmacological doses.
Vitamin D requires hydroxylation by the kidney to its
active form, therefore the hydroxylated derivatives
alfacalcidol or calcitriol should be prescribed if patients with
severe renal impairment require vitamin D therapy. Calcitriol
is also licensed for the management of postmenopausal
osteoporosis.
Paricalcitol p. 1148, a synthetic vitamin D analogue, is
licensed for the prevention and treatment of secondary
hyperparathyroidism associated with chronic kidney disease.
Vitamin E
The daily requirement of vitamin E (tocopherol) has not
been well defined but is probably 3 to 15 mg daily. There is
little evidence that oral supplements of vitamin E are
essential in adults, even where there is fat malabsorption
secondary to cholestasis. In young children with congenital
cholestasis, abnormally low vitamin E concentrations may be
found in association with neuromuscular abnormalities,
which usually respond only to the parenteral administration
of vitamin E.
Vitamin E has been tried for various other conditions but
there is little scientific evidence of its value.
Vitamin K
Blood and nutrition
Vitamin K is necessary for the production of blood clotting
factors and proteins necessary for the normal calcification of
bone.
Because vitamin K is fat soluble, patients with fat
malabsorption, especially in biliary obstruction or hepatic
disease, may become deficient. Menadiol sodium phosphate
p. 1150 is a water-soluble synthetic vitamin K derivative that
can be given orally to prevent vitamin K deficiency in
malabsorption syndromes.
Oral coumarin anticoagulants act by interfering with
vitamin K metabolism in the hepatic cells and their effects
can be antagonised by giving vitamin K.
Other compounds
Potassium aminobenzoate p. 1141 has been used in the
treatment of various disorders associated with excessive
fibrosis such as scleroderma and Peyronie’s disease. In
Peyronie’s disease there is some evidence to support efficacy
in reducing progression when given early in the disease;
however, there is no evidence for reversal of the condition.
The therapeutic value of potassium aminobenzoate p. 1141
in scleroderma is doubtful.
VITAMINS AND TRACE ELEMENTS ›
MULTIVITAMINS
PDF pages 1161, 1162
