Norketamine is the major metabolite (metabolic product) of the drug ketamine. Ketamine is a drug that is used as a treatment for depression or severe mental health conditions, although it is often misused recreationally. Norketamine is formed in the body after ketamine is taken.
From 
Drugs and Treatment Resources
References
Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.