The USP has fully promulgated the regulations for testing for elemental impurities in drug products, which will take full effect in January 2018. We’ve explored these regulations in past blog posts including Changes to Testing for Elemental Impurities in Drug Products, Risk Assessment for Elemental Impurities in Drug Products and Extractables & Leachables – Elemental Impurity Testing.
The FDA offers specific guidelines regarding elemental impurities in drug products. These guidelines include consideration for testing products as administered – oral, parenteral, or inhaled. These forms of administration have defined risk assessment limits; however, the dermal route of administration has not yet been addressed with formal guidance in relation to the Permitted Daily Exposure (PDE).
While many acknowledge that administration via the skin is the not same as oral administration, we commonly see products developed for dermal administration being compared in some fashion to oral PDE limits. The elements we test for, in our risk assessments, are commonly held to a fractional value of the PDE. According to ICH Q3D training documents, if an element is below 30% of the PDE limit, it is considered as very low risk and additional control strategies are not mandated.
In August of this year, the ICH IWG (implementation working group) prepared a concept paper with a work plan to develop PDEs for the Dermal route of administration for ICH Q3D. As of now, this will be handled as a maintenance process, and therefore, will not re-open the Q3D guideline. If the work plan is approved by the ICH Management committee, it is expected that the process would take roughly 18 months, resulting in a plan by the end of 2017.