Figure 1.

Structure of thalidomide enantiomers and packaging. A: Thalidomide is a stereo‐isomer and can exist in two enantiomeric states, depending on the state of the chiral carbon (see asterisk) allowing each form to have slightly different structural moieties. Both enantiomers, R and S, can rapidly interconvert (racemize) in body fluids and tissues and form equal concentrations of each form. B: Thalidomide was sold/distributed as a racemic mix of both enantiomers and called “Distaval” in the UK. These images are from an actual packet of “Distaval,” which was a Physician's Sample and given to women in early pregnancy. Note the safety advice on the packet. Reproduced from Vargesson, BioEssays, 2009,31,1327–1336.