Versatile and sensitive dual-detection HPLC method for rapid quantification of apomorphine hydrochloride: application to ex vivo percutaneous permeation and deposition studies utilising novel transdermal pressure-sensitive adhesive patches

Conventional delivery of apomorphine hydrochloride (APO) for management of ‘OFF’ periods in Parkinson’s disease is limited to subcutaneous or sublingual delivery, and would substantially benefit from a transdermal drug delivery system (TDDS). Minimal progression has been made thus far in this area, with current literature presenting debatably flawed or inconsistent experimental design for ex vivo percutaneous permeation and deposition studies, a crucial step in understanding TDDS performance. Provided here is an improved, robust, versatile and easily-transferred analytical methodology, fully validated in accordance with guidelines provided by the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). Reversed-phase high performance liquid chromatography (RP-HPLC) is employed with ultraviolet-visible (UV) light or fluorescence intensity (FID) detection in conjunction with a Franz diffusion-cell setup that ensures stability of APO and uses physiologically relevant neonatal porcine skin. Thus, this methodology may be reliably employed by future researchers developing an APO TDDS. To demonstrate application, a superficial investigation into model pressure-sensitive adhesive (PSA) patch systems provided sustained percutaneous delivery of up to 4.015 ± 2.361 µg/cm²/hr APO over a 24-hour period. These offer brief insight into a system that has yet to be studied in-depth for percutaneous delivery of APO, and highlight the importance of alternative penetration enhancers or enhancement techniques in developing a TDDS with clinical potential.