N-Acetyl-L-cysteine amide (NAC amide, CAS 38520-57-9) is a derivative of the amino acid L-cysteine, where the carboxyl group is amidated and the amino group is acetylated. This structural modification significantly enhances its lipophilicity and membrane permeability compared to its parent compound, N-acetylcysteine (NAC). Its primary application is in biomedical research and as a potential therapeutic agent. NAC amide is a highly effective cell-permeable precursor for intracellular glutathione (GSH) synthesis. It readily crosses cell membranes and is hydrolyzed to release L-cysteine, a rate-limiting substrate for GSH production. This property makes it a powerful research tool for studying oxidative stress, neuroprotection, and mitochondrial function. It is investigated for its potential in models of neurodegenerative diseases, ischemia-reperfusion injury, and other conditions associated with glutathione depletion and oxidative damage. Due to its enhanced stability and delivery compared to NAC, it is also explored in the context of advanced drug formulations and as a functional ingredient in nutraceuticals. Its role as a direct antioxidant and a crucial regulator of cellular redox status underpins its broad research utility in life sciences.