Homocystine is the double-bonded form of homocysteine but it occurs only transiently before being converted to the harmless cystathionine via a vitamin B6-dependent enzyme. Homocystine and homocysteine-cysteine mixed disulfide account for >98% of total homocysteine in plasma from healthy individuals.

[Des-Tyr1]-gamma-Endorphin is a neuropeptide, which can be found in human cerebrospinal fluid. [Des-Tyr1]-gamma-Endorphin exhibits antidepressant efficacy, facilitates the extinction of active avoidance and attenuates the passive avoidance behavior in rats.

Loperamide oxide (R 58425) is a secreted antidiarrheal agent that increases peristalsis and inhibits intestinal absorption of water and ions and is used in the study of chronic diarrhea in patients with Crohn's disease.