Concurrent administration of water-soluble vitamin E can increase the oral bioavailability of cyclosporine a in healthy dogs.

Randomized crossover studies were performed to determine the effect of coadministration of d-alpha-tocopheryl polyethylene glycol 1,000 succinate (vitamin E TPGS) on the oral bioavailability of cyclosporine A (CsA) formulated as either Sandimmune (Novartis Pharmaceuticals) or Neoral (Novartis Pharmaceuticals). Healthy dogs were given a single oral dose of each cyclosporine formulation with and without vitamin E TPGS. Blood samples were collected from each dog before and at various intervals for 24 hours after drug administration. Whole-blood CsA concentrations were determined by high-pressure liquid chromatography. Noncompartmental pharmacokinetic analysis showed that coadministration of vitamin E TPGS increased the oral bioavailability of Sandimmune. The bioavailability of Neoral was greater than that of cyclosporine. Concurrent administration of vitamin E TPGS had no consistent effect on the bioavailability of Neoral.