Pharmacokinetics of a single intramuscular injection of vitamin E to premature neonates.

The pharmacokinetics of parenterally administered vitamin E (d, l-alpha tocopherol) in serum were developed using data from five premature neonates (1,500 +/- 100 gm) receiving a single 20 mg/kg intramuscular injection. Blood samples were obtained immediately prior to drug administration to establish baseline vitamin E concentrations: then further sampling was performed at various intervals for up to 7 days. It was assumed that dietary intake of vitamin E did not markedly alter serum concentration of vitamin E during the 7-day study and that the total intramuscular dose was absorbed. Although extensive sampling could not be performed in any one neonate, composite sampling from the study population made it possible to construct a pharmacokinetic profile of vitamin E in premature neonates. The half-life of elimination was 44 hours, the volume of distribution (V beta) was 0.41 liter/kg. and serum clearance was 6.5 ml/hr/kg. Vitamin E is an important biological antioxidant that may provide protection to the retinas and lungs of premature infants exposed to supplemental inspiratory oxygen. Therefore, if the pharmacokinetics of vitamin E observed in the present study can be generalized to the population of premature infants, a single 10 mg/kg intramuscular (IM) loading dose followed by 5 mg/kg every 48-72 hours should maintain serum concentration of 1.5 to 2.5 mg%--a level that has been associated with antioxidant protection.