Abstract: A device for the transdermal delivery of a pharmacologically active substance has first and second superimposed mutually contacting adhesive layers (2, 3). The first layer (3) is in use brought into contact with the skin. The active substance is dissolved in both layers, the affinity of the first layer for the active substance being between about 1.15 and about 10 times lower than that of the second layer. The percent saturation of the active substance in both the layers is the same and is less than 100%. The first layer has a greater thickness than the second layer. The device is simple and can provide stable delivery over a long period.

Abstract: A steroid is used as an additive in manufacture of a transdermal drug delivery device, to act as a crystallization inhibitor inhibiting crystallization, during storage of the device, of an active drug in the form of a hormone which has a pharmaceutical or physiological effect in use of the device. The crystallization-inhibiting steroid is present in the device in an amount insufficient to provide significant pharmaceutical or physiological effect in use of the device.