N-Acetyl-L-Cysteine (free-form / USP)
N-Acetyl-L-Cysteine (free-form / USP) is a tier 1 form of N-Acetylcysteine (NAC), used in 1,551 on-market products .
1,551
on-market products
tier 1
quality tier
n/a
elemental fraction
Why this tier: The only form used across essentially the entire NAC clinical trial literature (respiratory, psychiatric, hepatoprotective); "free-form"/"USP" label notes describe purity/manufacturing standard, not a chemically distinct form.
Source: Zheng JP et al. 2014, Lancet Respir Med 2(3):187-94, PMID 24621680