In a therapeutic system such as a plaster for administration of an active compound through the skin and comprising a covering layer which is essentially impermeable to the active compound, an active compound reservoir layer and a protective layer which can be pulled off and which is essentially impermeable to the active compound, the improvement wherein the reservoir layer contain about 1-30% of active compound in an elastomer mixture comprising a predominantly amorphous olefinic (co)polymer with a glass transition temperature of