N-Acetyl-L-Cysteine
Product Name : N-Acetyl-L-Cysteine         
Other Names: N-Acetyl-L-(+)-cysteine
CAS number : 616-91-1
Molecular Formula: C₅H₉NO₃S
Molecular Weight: 163.19500.
Appearance/Color : White powder
Applications : medicine         

N-acetyl cysteine is an antioxidant that might play a role in preventing cancer. As a drug, it's used by healthcare providers to treat acetaminophen (Tylenol) poisoning. It works by binding the poisonous forms of acetaminophen that are formed in the liver.

It can be taken any time of day that is most convenient.  NAC is available in 500-, 600-, 750- and and 1,000-milligram tablets.  You will likely need to divide up your dose and take it twice or three times daily to see results, so consider taking it once it in the morning and again at night.