ASCORBIC

Adults, the elderly and children over 12 years:

One to five tablets daily in divided doses.

Children aged 4 – 12 years:

Half to two and a half tablets daily in divided doses.

Note:

As the dietary intake of vitamin C may be less in the elderly, they are at greater risk of being deficient in this vitamin.

Large doses of ascorbic acid may cause diarrhoea. Patients known to be at risk of hyperoxaluria should not ingest ascorbic acid in doses exceeding 1 gram daily, as there may be increased urinary oxalate excretion. However, such a risk has not been demonstrated in normal, non-hyperoxaluric individuals.

Ascorbic acid has been implicated in precipitating haemolytic anaemia in certain individuals with a deficiency of glucose-6-phophate dehydrogenase. Increased intake of ascorbic acid over a prolonged period may result in an increase in renal clearance of ascorbic acid, and deficiency may result if the intake is reduced or withdrawn rapidly.

Doses of more than 600mg daily have a diuretic effect.

g. Labstix, Testape) and false positive results with neocuproin methods. Estimation of uric acid by phosphotungstate or by uricase with copper reduction and measurement of creatinine in non-deproteinised serum may also be affected. High doses of vitamin C may give false-negative readings in faecal occult blood tests.

Ascorbic acid supplements should not be given to patients with hyperoxaluria.