Biopharmaceutic factors in parenteral administration of vitamin E.

When properly formulated, micellar-type aqueous dispersions of tocopheryl acetate are administered intravenously or intramuscularly to dogs, the rate-limiting step in the bioavailability of the physiologically active free tocopherol is the rate of hydrolysis of the acetate ester. A similar dispersion of free tocopherol yields blood levels of tocopherol many fold higher than those obtained with the acetate ester after intravenous injection and also yields much greater increases in blood levels of free tocopherol after intramuscular injection than the acetate ester formulation, particularly in the early period after the dose.