Disposition of intravenously administered pharmacologic doses of vitamin E in newborn rabbits

Newborn rabbits were given a single intravenous dose (100 mg/kg) of either alpha-tocopherol or alpha-tocopheryl acetate to compare disposition characteristics of these two forms of vitamin E. The resulting tissue concentrations of alpha-tocopherol and alpha-tocopheryl acetate differed significantly. Tissue concentrations of either form of vitamin E were much higher than those provided by normal nutrition, and remained unchanged (except in the liver) for 6 days after dose. alpha-Tocopheryl acetate was not completely converted to alpha-tocopherol, and only 50% of the dose was recovered 3 days after administration. The entire dose of alpha-tocopherol was recovered intact 3 days after administration. The persistence of very high tissue vitamin E concentrations after a single intravenous dosing, the disappearance from the body of half of the administered dose of alpha-tocopheryl acetate, and the lack of complete conversion of alpha-tocopheryl acetate to alpha-tocopherol when given intravenously have profound implications regarding the current clinical practice of giving repeated pharmacologic doses of vitamin E to newborn infants.