Na-R-lipoic acid is better absorbed than R-lipoic acid

[NHE]

The sodium salt of r-lipoic acid is better absorbed than regular r-lipoic acid (which is unstable and easily polymerizes).

The plasma pharmacokinetics of R-(+)-lipoic acid administered as sodium R-(+)-lipoate to healthy human subjects
Altern Med Rev. 2007 Dec;12(4):343-51.

Different forms of RLA produce dramatically different PK values. Recently, RLA was compared to NaRLA in humans using a simple crossover design.⁴³ This study compared Cmax and AUC values of a pre-dissolved aqueous solution containing 600 mg RLA (as NaRLA) to those of 600 mg RLA in the same subjects. In a single male (subject 1), NaRLA produced Cmax of 14.1 mcg/mL; whereas, RLA resulted in a Cmax of 0.7 mcg/mL (increase of 25.86x). The AUC in the same subject was 5.18 mcg hr/mL for NaRLA versus 1.56 mcg hr/mL for RLA (increase of 3.3x). In a single female (subject 4), Cmax was 18.1 mcg/mL for NaRLA versus 1.01 mcg/mL for RLA (increase of 17.9x) and the AUC was 5.71 mcg hr/mL for NaRLA compared to 2.14 mcg hr/mL for RLA (increase of 2.67x).

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PS - Pay no attention to figure 1 supposedly depicting the molecular structures of R and S lipoic acid. It's incorrect. Here are the correct structures. The upper structure is R-Lipoic acid and the lower structure is S-Lipoic acid. The bonds represented by solid a wedge comes out of the plane of the page. The bond represented by a dashed wedge goes into the plane of the page. In essence, the two molecules are mirror images of each other.

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