| abstract |
A compound of formula (I), or a pharmaceutically acceptable salt thereof, in which. R1 and R2 independently represent C1-4 alkyl or difluoromethyl, provided that at least one of R1 and R2 represents difluoromethyl; R3 represents H, F, Cl or Br; and X and Y independently represent C> = O or CH2, provided that at least one of X and Y represents C> = O. |