Challenges in setting permitted daily exposure limits for pharmaceuticals: A review

BACKGROUND: When more than one drug is manufactured at a shared facility or equipment in pharmaceutical manufacturing, the potential carry-over of the retained residue of existing drug product on product contact parts of the equipment to the next product can be a source of cross contamination. Permitted daily exposure (PDE) is derived based on the complete nonclinical and clinical data available and is a dose that is unlikely to cause adverse effects if an individual is exposed, by any route, at or below this dose every day over a lifetime. OBJECTIVE: The objective was to present a comprehensive review of available scientific knowledge for derivation of PDE. METHODS: PubMed and ScienceDirect databases were searched using keywords “PDE” and “pharmaceuticals” and all the relevant literature up to March 2021 was reviewed. We have also calculated PDEs for Tobramycin (CAS No. 32986-56-4) and Acetyl Salicylic Acid (ASA, CAS No. 50-78-2). RESULTS: This research will be useful for scientists working in the PDE domain. The given examples emphasize the importance of use of human data in calculating PDE. CONCLUSION: The duty of the risk assessor entrusted with setting PDEs is to derive a data driven, scientifically justified value that is safe for patients, while avoiding unjustified conservativeness that puts unnecessary burden on manufacturing.