The pharmacokinetics of vitamin K(1) was studied in 21 newborn infants. 11 neonates had received no parenteral loading dose prior to the study (group I), while 10 had been injected 5-10 mg vitamin K(1), at birth (group II). At postnatal age 2-9 h, 1 mg of vitamin K(1) was injected intravenously, and small samples of blood (≤ 500µl) were collected at different times during 6 h. Serum vitamin K(1) and its epoxide were assayed by high-performance liquid chromatography (HPLC). In both groups, the disappearance curve showed two exponential components: a fast distribution component during the 1 st h and a slower elimination component during the next 5 h. In group I, the plasma half-life of the first component was between 18 and 52 min (median 23 min), and the half-life of the second was between 67 and 179 min (median 109 min). Both half-lives were significantly higher in group II. The volumes of distribution were suggestive of distribution into plasma during the first phase and roughly into the extracellular water for the second component. Epoxide was detected in most patients 15 min after vitamin K(1) injection, and after 3 h its concentration was higher than the concentration of vitamin K(1). These data suggest that the kinetics of vitamin K(1) in neonates is not very different from that in adults. The newborn infant is able to oxidize vitamin K(1), a phenomenon in keeping with the gamma carboxylation of glutamic acid.
Reference intervals for normal concentrations in blood of vitamins B1, B2, E, D, retinol, beta-carotene, and folic acid were determined from a selected sample of people attending a Health Examination Center or being examined in occupational health services in France. This reference sample consisted of 362 men and women, ages 18 to 44 years, selected according to the main variation factors known for the vitamins studied: consumption of tobacco and alcohol, ponderal index (relating height and weight), use of drugs and oral contraceptives, and past history of surgical or medical treatment. Reference intervals were determined for each sex. Vitamin B1 (erythrocyte transketolase activity), plasma retinol, and folic acid values in whole blood are significantly higher in men than in women (p less than 0.001), but vitamin B2 (activation of erythrocyte glutathione reductase) and plasma beta-carotene values are significantly higher in women (p less than 0.001 and less than 0.01 respectively). Dietary intake of vitamins produced no significant displacement of the reference values. For each vitamin we discuss the other major sources of variation factors and the usual values reported in the literature.
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