Quality Control for Incoming Raw Materials Beyond Identity and Purity: Case Studies from Recent Merck API Manufacturing Processes

The development of robust manufacturing processes for active pharmaceutical ingredients (APIs) is paramount to ensure a supply of safe and effective medications. Implementation of a holistic control strategy, including quality control of incoming raw materials, is a key element in meeting this goal. This paper describes several examples from recent Merck API manufacturing routes, in which impurities in raw materials affected the processes in various ways, including giving rise to new process impurities, jeopardizing process safety and causing damage to reaction vessels, and─sometimes unexpectedly and counterintuitively─suppressing formation of process impurities. In all of these examples, analytical characterization plays a critical role in identifying these impurities and enabling their control to ensure consistent process performance and product quality.