Quality by design approaches for topical dermatological dosage forms

The quality of a pharmaceutical dosage form is the foremost criterion during the development of a product. The quality by testing (QbT) technique used by the pharmaceutical industry to ensure the quality of a drug product is a rigid process with tight specifications. The specifications set by QbT are not essentially based upon the critical quality attributes of the materials and critical process parameters involved in development, but based upon recorded observation of manufactured batches. Room for flexibility is narrow as every level change requires submission of a supplement to the US Food Drug and Administration. Unlike QbT, the concept of quality by design (QbD) is a modern approach to ensure the quality of pharmaceutical products. It can identify the critical attributes of the material and the process parameters involved in development of the drug product through substantial scientific understanding with an established design space. QbD tools such as design of experiment, risk assessment, and process analytical technology help to establish a control strategy for every drug product with an option of continual monitoring and improvement for a quality drug product. Implementing the concept of QbD to topical dermatological dosage forms is in the initial stages. For a generic topical dermatological dosage form, establishing the required pharmaceutical and therapeutic equivalence with same components or qualitatively (Q1), same components with same concentration or quantitatively (Q2), and same components in same concentration with same arrangement (Q3) is a cumbersome process. Applying QbD approaches by defining a quality target product profile and identifying critical quality attributes with establishment of a design space and control strategy can guide the design of a quality-based generic topical dermatological product.