Investigations on the pharmacokinetics of alpha-lipoic acid in healthy volunteers.

The aim of the present study was to examine the pharmacokinetics of racemic alpha-lipoic acid in twelve healthy volunteers following single oral administration of 200 and 600 mg (Thioctacid 200 film tablets).Each film tablet contained 200 mg of alpha-lipoic acid. In addition, an injection solution containing 200 mg of alpha-lipoic acid was administered. Plasma concentrations of alpha-lipoic acid were determined using a validated reversed-phase HPLC method with electrochemical detection having a lower limit of quantitation of 1 ng/ml. The areas under curve (AUC) were 46.82 +/- 21.46 and 157.97 +/- 35.05 microg x min/ml for the oral and intravenous administration of 200 mg, respectively.The AUC following oral administration of 600 mg was 157.83 +/- 35.82 microg x min/ml. The difference in mean t(1/2) for the two oral doses and the i.v. dose (in the range of 25.3-32.7 min) was not statistically significant.The lack of a significant difference between values for apparent total plasma clearance for the 200 and 600 mg doses indicates non-saturable kinetics of alpha-lipoic acid in healthy volunteers in this dose range. The absolute bioavailability after the 200 mg dose was 29.1 +/- 10.3%.