Thalidomide (C13.H10.N2.O4) molecular model. The atoms are colour-coded: carbon (yellow), hydrogen (white), nitrogen (green) and oxygen (pink). This is S-thalidomide, a mirror image (enantiomer) of R-thalidomide, both of which share the same structural formula. Thalidomide was developed as a sedative drug to aid sleep in pregnant woman. It was found to cause foetal abnormalities (stunted limbs, or phocomelia), and was withdrawn in 1961. Further research discovered that only the S" form caused deformities. A purified drug containing only the "R" enantiomer is now being used to treat leprosy and as an anti-cancer drug. See A624/158 for an image of R-thalidomide."