8 DECEMBER, 2020OPINIONTransdermal drug delivery systems (TDDS) are combination products clas-sified as such due to their dual function as medical devices and pharmaceuticals. For example, medical device characteristics of a TDDS include adherence to the user for the du-ration of the wear time, control of adhesive flow from the perimeter of the system while in use (cold flow), and occlusion of the drug-containing system to prevent unintended exposure. Pharma-ceutical characteristics of a TDDS include prod-uct potency and drug delivery rate, for example. To maintain the integrity of these complex combi-nation systems, the developers of the system must explicitly define what attributes are critical to the quality (i.e., blend uniformity, patch dimensions, or patch delivery rate). It is the responsibility of the manufacturer to ensure then they can con-trol their process appropriately to maintain these product critical quality attributes (CQA). A Qual-ity by Design (QbD) approach to TDDS develop-ment ensures that the critical process parameters A QUALITY APPROACH TO COATING TRANSDERMAL DELIVERY DEVICESBy Robert Lambert, Director of Manufacturing Technical Services, Noven Pharmaceuticals
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