Bioavailability of intramuscular vitamin E acetate in rabbits

The bioavailability of α-tocopherol acetate and α-tocopherol (vitamin E) was assessed in male rabbits given 50 mg kg^-1 doses according to a randomized design. After intramuscular injection of α-tocopherol acetate in colloidal aqueous solution, a mean absolute bioavailability of 65% was calculated for the acetate and 35% for the physiologically active compound, α-tocopherol. Comparison of the kinetic profiles after intravenous and intramuscular administration of the acetate and intravenous injection of α-tocopherol, revealed absorption of α-tocopherol acetate from the site of injection and hydrolysis of the acetate to be potential limiting steps in the bioavailability of α-tocopherol. Intramuscularly injected α-tocopherol acetate in olive oil (the only formulation available in a few European countries) proved completely bio-unavailable. It thus appears necessary to re-assess the utility of current vitamin E supplementation, since the only formulations available offer poor bioavailability.