The invention relates to a transdermal or topical plasters that contain active ingredient comprising a non occlusive back layer a matrix composed of one or more polymer layers having at least one pharmaceutical active ingredient in one or more of the layers wherein the structure forming base polymers of the layer(s) are non occlusive or only slightly occlusive and a second polymer that has a low water vapor permeability and that is immiscible or only very slightly miscible with the base polymer is dispersed in at least one of the polymer layers.
