Thalidomide
Thalidomide was developed in the 1950s to prevent nausea during pregnancy and for use as a sleeping pill. However it was banned in the early 1960s after it was found to cause limb abnormalities in the children of women who took it during pregnancy.
- Taking only one dose of thalidomide early in pregnancy was found to severely affect the growth of foetal limbs (arms, legs, hands, and feet). It also put the foetus at risk of other injuries, including eye and ear defects and severe internal defects of the heart, genitals, kidneys, digestive tract (including lips and mouth), and nervous system.
Laboratory tests showed that in some animals the 'R' enantiomer was tetragenic (caused abnormalities) but the 'S' isomer was an effective sedative. Further research has shown that even if a stereoselective sample of thalidomide (only one optical isomer present) is administered body pH can cause racemisation. The means that both enantiomers are formed in a roughly equal mix in the blood.
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'R' Thalidomide |
'S' Thalidomide' |