is a progestin
used in hormonal contraceptives
. Norgestrel is a mixture of two stereoisomers
, dextro-norgestrel (CAS# 797-64-8) and levo-norgestrel (CAS# 797-63-7). Only levonorgestrel
is biologically active. Therefore, while some medications may contain dextronorgestrel, they are often labeled in terms of their levonorgestrel content only, ignoring the inert isomer.