Synonyms:
13-ethyl-17alpha-hydroxy-18,19-dinorpregn-4-en-20-yn-3-one butyrate ; 13-ethyl-17α-(1-oxobutoxy)-18,19-dinorpregn-4-en-20-yn-3-one ; (17alpha)-13-ethyl-17-(1-oxobutoxy)-18,19-dinorpregn-4-en-20-yn-3-one ; levonorgestrel butyrate ; 18,19-dinorpregn-4-en-20-yn-3-one,13-ethyl-17-(1-oxobutoxy)-, (17a)-