/uy'soh tri tin"oh in, -oyn/ , n. Pharm.
a yellowish-orange to orange crystalline powder, C 20 H 28 O 2 , used in the treatment of cystic acne.
[ ISO- + tretinoin a name for retinoic or Vitamin A acid, equiv. to t- (of uncert. derivation) + retino ( ic acid ) (RETIN(OL) + -O- + -IC) + -IN 2 ]