The present invention concerns a transdermal therapeutic system, comprising a backing layer, which is not permeable for the active ingredient, and a matrix layer on one side of the backing layer, wherein the matrix layer contains at least one pressure sensitive adhesive and ketamine or a pharmaceutically acceptable salt or solvate thereof, wherein the at least one pressure sensitive adhesive has free hydroxyl groups, as well as its use as medicament, in particular for the treatment of depression and pain.