Kopexil (INCI name diaminopyrimidine oxide, trade name Aminexil) is a chemical compound used to increase the volume of hair in the growth stage by working on the deep structure of the roots. It rejuvenates the hair roots so that healthy hair growth can persist. The perifollicular fibrosis is a condition in which collagen around the roots becomes rigid, tightens, and pushes the hair out. Kopexil helps in softening of the collagen. Kopexil is not approved for use as a drug in the United States or in Europe.

Mechanism of action
The exact mechanism of action of kopexil is unknown. There is no proof of therapeutic effect for kopexil against alopecia