Modeling and design of transdermal drug delivery patches containing an external heating device

Process modeling and design concepts were implemented to aid in the manufacturing of heat-enhanced transdermal drug-delivery systems. The simulated prototype consists of a corticosterone-loaded polymer patch applied to the skin and connected to a heating device in which an exothermic reaction occurs. To achieve a desired transdermal flux of 1.2 × 10−5 mg/cm2 h, this contribution focuses on the influences of the (1) initial reaction rate (−rA0), (2) mass of filler material in the device (m), (3) initial concentration (C0) of medicament in the patch and (4) overall heat transfer coefficient (U). A regression technique yielded the following results: −rA0 = 3.000 × 10−2 kg/m3 s, m = 1.251 × 10−8 kg, U = 6.124 × 10 J/m2 K s and C0 = 1.966 × 10−1 kg/m3. When m was fixed at 12.5 g, the optimum design required the following specifications: rA0 = 2.765 × 10−2 kg/m3 s, U = 1.402 × 103 J/m2 K s and C0 = 1.941 × 10−1 kg/m3. The priority (Si) of the input factors (i  ) in reaching the target delivery rate is: SC0>S−rA0>Sm>SUSC0>S−rA0>Sm>SU.