b12

March 5, 2005

Causes of folate deficiency Folic acid is found in many food types,

with the majority provided by green vegetables and offal. It is easily

destroyed by cooking, unlike vitamin B12 which is not. It is absorbed

in the small intestine and adults require 100mcg daily, with a Western

diet providing 200mcg per day. Unlike vitamin B12 and iron, body stores

of folate are small and deficiencies can occur more readily, within

four months of decreased intake or increased requirements.

There are many causes of folate deficiency, but the most common is due

to a low intake. Also, importantly for pharmacists, some drugs are

implicated in reducing folate levels. Prophylactic folic acid is

warranted in conception and pregnancy due to its role in the prevention

of neural tube defects.

Treatment This depends on the type of deficiency present. If a

patient receives folic acid as a sole therapy for an undiagnosed

vitamin B12 deficiency, then neuropathy may result, leading to subacute

spinal degeneration. In both cases of folate and vitamin B12

deficiency, any underlying cause should be established and treated

where possible. In vitamin B12 deficiency, therapy is intramuscular.

Oral treatment is unlikely to work as the majority of cases in the UK

are either due to pernicious anaemia and the associated reduction in

intrinsic factor, or more commonly malabsorption. Treatment is 1mg of

intramuscular hydroxocobalamin repeated five times at intervals of two

to three days in order to replenish depleted body stores. The patient

is then maintained on 1mg of hydroxocobalamin intramuscularly every

three months. The patient should be informed that treatment is likely

to be for life.

In folate deficiency, oral supplementation of 5mg of folic acid for

four months is usually all that is required. Treatment is usually

short-term as the causes of folate deficiency are self-limiting. Higher

doses may be required occasionally, especially in malabsorption

conditions.

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