As nouns the difference between thalidomide and phthalidomide
is that
thalidomide is (pharmaceutical drug)
oxopiperidin-3-yl)-1h-isoindole-1,3(2h)dione —
c13h10n2[[oxygen|o4 — a drug that was sold during the late 1950s and 1960s as a sleeping aid, and to pregnant women as an antiemetic to combat morning sickness and other symptoms, but was withdrawn after being proven to cause severe birth defects, such as phocomelia; currently used to treat leprosy while
phthalidomide is alternative spelling for thalidomide.