Bioavailability of intramuscular vitamin E acetate in rabbits.
The bioavailability of alpha-tocopherol acetate and alpha-tocopherol (vitamin E) was assessed in male rabbits given 50 mg kg-1 doses according to a randomized design. After intramuscular injection of alpha-tocopherol acetate in colloidal aqueous solution, a mean absolute bioavailability of 65% was calculated for the acetate and 35% for the physiologically active compound, alpha-tocopherol. Comparison of the kinetic profiles after intravenous and intramuscular administration of the acetate and intravenous injection of alpha-tocopherol, revealed absorption of alpha-tocopherol acetate from the site of injection and hydrolysis of the acetate to be potential limiting steps in the bioavailability of alpha-tocopherol. Intramuscularly injected alpha-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.
Pedraz
J L
JL
Laboratory of Clinical Pharmacology, Instituto di Ricerche Farmacologiche Mario Negri, Milano, Italy.
Calvo
B
B
Bortolotti
A
A
Celardo
A
A
Bonati
M
M
D000818:Animals; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D008297:Male; D011817:Rabbits; D024505:Tocopherols; D014810:Vitamin E / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D014810:Vitamin E; D024502:alpha-Tocopherol; D024505:Tocopherols