Concentration of 25-hydroxyvitamin D in serum of infants under the intermittent high-dose vitamin D3 prophylactic treatment.

The concentration of 25-hydroxyvitamin D was measured in serum of 90 healthy and 123 sick infants. The mean concentration of 25-OH-D in the group of healthy infants given intermittent prophylactic doses of vitamin D3 was 44.0 microgram/l and was nearly three times higher than the average concentration in healthy adults not given any vitamin D substitution. In the 123 clinically treated infants the average 25-OH-D concentration was 86.2 microgram/l, and 59.4% of infants had values over 40 microgram/l. In the subgroup of infants admitted to the hospital because of diarrhea, lower values were found than the average ones of clinically-treated infants. Two children with clinical rickets had very low 25-OH-D concentrations. The 25-OH-D half life in serum of infants varied from 19 to 27 days and single dose--300,000 IU (7.5 mg) of vitamin D3 was found to assure a sufficient 25-OH-D concentration in serum for as many as 190 days. It is concluded that high intermittent oral doses of vitamin D3 give an effective protection against rickets but at the cost of several times higher 25-OH-D concentration in serum and at the risk of hypervitaminosis D in some healthy infants.