What is "trimegestone"

n. A steroidal progestin.

Trimegestone ( INN) (brand name Ondeva), also known as 21-hydroxypromegestone, is a 19-norprogesterone derivative and steroidal progestin which was introduced in France in 2001 and is used as a hormonal contraceptive and in hormonal replacement therapy for postmenopausal symptoms. It is a very potent and pure progestogen and is the most potent progestin of the 19-norprogesterone group (clinically effective in endometriosis at only 0.1 mg/day). The drug has little activity at other steroid hormone receptors, and in accordance, possesses no androgenic, antiandrogenic, or glucocorticoid properties. However, it is said to have weak antimineralocorticoid activity. The metabolites of trimgestone are active and have similar properties to the parent drug.

Trimegestone has been described as both "fourth generation" and "second generation" (due to the use of different progestin generational schemes; in any case, it is considered to be of the most recent generation).