Pharmacokinetics of different formulations of tioctic (alpha-lipoic) acid in healthy volunteers.

This study was designed to evaluate in healthy volunteers plasma and cellular (in erythrocytes) of three formulations of alpha-lipoic acid (ALA) available in Italy with different rates of absorption, two with a claimed high absorption rate (Byodinoral 600 QR, Tiocronal 600 HR) and one with a claimed prolonged absorption rate (Tiobec 600 retard). These formulations were compared with the registered ethic formulation of the compound (Thioctacid 600 mg HR), available in Germany. Area under the curve from time 0 to last measured time (AUC(t)), peak plasma concentration (C(max)) of ALA, and time (T(max) ) at which C(max) was observed were the plasma kinetic parameters measured. Concentration of ALA at different sampling times was the only parameter assessed for erythrocytes. The AUC(t) values were similar for the four formulations of ALA tested. C(max) was significantly higher for Byodinoral 600 QR, Tiocronal 600 HR compared to Thioctacid 600 mg HR or Tiobec 600 retard, whereas T(max) value was significantly shorter for Byodinoral 600 QR in the order by Tiocronal 600 HR, Thioctacid 600 mg HR, and Tiobec 600 retard. ALA concentrations that accumulated in erytrocytes after the administration of the different formulations of the antioxidant are directly proportional to the plasma levels of each formulation. Because antioxidant capabilities of ALA depend on the glutathione regeneration the compound induces in cells, the most rationale approach for eliciting antioxidant activity at the cellular level is probably in the use of a formulation allowing the compound to reach its target at highest concentrations and in the shortest time.