Tissue vitamin E levels in newborn rabbits after pharmacologic dosing. Influence of dose, dosage form, and route of administration.

Tissue levels of alpha-tocopherol and alpha-tocopheryl acetate were measured in neonatal rabbits using high-performance liquid chromatography after administration of 100 mg/kg once or daily of either alpha-tocopherol or alpha-tocopheryl acetate subcutaneously, orally, or intravenously. Tissues were analyzed at 1, 3, and 6 days after daily dosing was begun. Tissue levels of alpha-tocopherol increased after each dose of alpha-tocopherol; the liver had much higher concentrations than other tissues after subcutaneous or oral administration. Alpha-tocopherol and alpha-tocopheryl acetate given orally produced similar tissue levels of alpha-tocopherol. Intravenous administration of alpha-tocopherol resulted in high concentrations of alpha-tocopherol in the liver, whereas intravenously administered alpha-tocopheryl acetate produced high concentrations of alpha-tocopheryl acetate in the lung. Following intravenous administration of alpha-tocopheryl acetate, only 2-4% of the total vitamin E present in the lung was alpha-tocopherol. From these results we conclude that total dose, dosage form, and route of administration of vitamin E have major influences on tissue vitamin E levels and whether the predominant molecular form is alpha-tocopherol or alpha-tocopheryl acetate. Assuming vitamin E tissue levels and molecular form determine tissue antioxidant activity, total dose, dosage form, and route of administration of vitamin E affect the potential clinical benefits that may result from pharmacologic vitamin E therapy in newborn infants.