The biological activities of norgestrel and its enantiomers.

The dextrorotatory enantiomer of norgestrel has now been tested by oral and parenteral routes in a broad range of biological assays and its inactivity has been confirmed. The active enantiomer has been further compared with the racemate in a similarly broad range of tests, largely by the oral route. Levonorgestrel was twice as potent as the racemate in experiments in which norgestrel was effective. These data reinforce earlier findings that levonorgestrel is responsible for all the biological activity found in norgestrel.