l-cysteine , acetylcysteine , ethylcysteine and mecysteine lowered the potencies of almost all of the antibiotics at high concentrations ( 500 mcg/ml ) , but at low concentrations ( 12.5 mcg/ml ) , mecysteine lowered the potencies of only three antibiotics and l-cysteine those of only four antibiotics , while acetylcysteine decreased the potencies of six and ethylcysteine those of seven antibiotics .
C0010654
l-cysteine
C0001047
acetylcysteine