N-acetyl-L-cysteine and vitamin C are frequently taken together, however, the two supplements should never be taken together. One of the selling points of taking the two supplements together was that N-acetyl-L-cysteine would prevent the oxidation of vitamin C to dehyrdroascorbate which N-acetyl-L-cysteine very effectively does. However dehyrdroascorbate is the form of vitamin C absorbed via glucose transporters. Preventing the oxidation of vitamin C with N-acetyl-L-cysteine is a huge error. There are many grounds for not supplementing N-acetyl-L-cysteine. The high effectiveness of N-acetyl-L-cysteine in preventing oxidation of vitamin C is one.
Supplemetantion that increases extracellular L-cysteine by decreasing levels of extracellular cystine, as do n-acetyl-l-cysteine and lipoic acid, must be avoided. Cystine, has to be available to enter cells via the cystine/glutamate antiporter so l-glutamate can be transported out. Any supplement that decreases extracellular cystine levels is very dangerous. Blocking the cystine/glutamate antiporter induces ferroptosis which can kill cells.