The present invention pertains generally to the field of transdermal drug delivery. More specifically, the invention relates to a device for the transdermal delivery of an alkaline pharmaceutically active compound that is susceptible to degradation in its free base form (e.g., rivastigmine) that comprises an adhesive matrix layer, a backing layer and a release or protective layer, wherein the adhesive matrix layer comprises said pharmaceutically active compound, triethylcitrate and hydrochloric acid. The invention also relates to methods of preparing such devices.