Bioavailability of intramuscular vitamin E acetate in rabbits

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Abstract
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.