From the LEF forum:
"The half-life of alpha lipoic acid varies between individuals somewhat, but it generally around 1/2 hour.
Eur J Pharm Sci 1999 Apr;8(1):57-65
Dose-proportionality of oral thioctic acid–coincidence of assessments via
pooled plasma and individual data.
Breithaupt-Grogler K, Niebch G, Schneider E, Erb K, Hermann R, Blume HH, Schug BS, Belz GG
Center for Cardiovascular Pharmacology, Mathildenstrasse 8, 55116, Mainz,
Thioctic acid (TA), a racemate of R-(+)- and S-(-)-enantiomers of alpha-lipoic
acid, acts as a powerful lipophilic, free-radical scavenger and is used in the
treatment of diabetic neuropathy. This trial investigated the dose-linearity of
enantiomer pharmacokinetics following the oral administration of single doses of
50 to 600 mg TA (formulation provided by ASTA (Medica)) in healthy volunteers.
TA enantiomer concentrations in individual and pooled plasma samples were
determined using enantioselective, high-performance liquid chromatography. TA
was rapidly absorbed (tmax, 0.5 to 1 h). Maximum plasma concentrations (Cmax) of
the R-(+)-enantiomer were about 40-50% higher than those of the S-(-)-enantiomer
(50 mg: 135.45 ng/ml R-(+)-TA, 67.83 ng/ml S-(-)-TA; 600 mg: 1812.32 ng/ml
R-(+)-TA, 978.20 ng/ml S-(-)-TA; geometric means). The decline observed in the
plasma concentration was steep (t1/2, 0.5 h). The dose-linearity and
proportionality of pharmacokinetic parameters could be demonstrated on an
intra-individual basis and for the group geometric means. An analysis of pooled
plasma samples proved to be a suitable means for deriving reliable first-sight
results prior to individual assessments.
PMID: 10072479, UI: 99172305 – Tom]"
This might not be acurate if plama concentrations are not be an accurate indicator e.g. if it is being “sequestered” outside the plasma. Jarrow brand (no commercial interest) does make a time releasse 250 mg ALA, but as I recall they said it dissolved over several hours.