Table III.

Important API and Excipient Attributes Relevant to Excipient Compatibility Studies

Important API Attributes relevant to Excipient Compatibility Studies	Important Excipient Attributes relevant to Excipient Compatibility Studies
API Impurity Profile (lot specific): water, solvent, metals and amorphous content, acidic/basic impurities, process-related impurities, alternate forms of the API present in small quantities (free forms or higher energy polymorphic forms)	Excipient impurity profile (lot specific): water, solvent, metals, amorphous content, acidic/basic impurities, reactive impurities (peroxides, aldehydes, organic acids)
Thermal and thermal/humidity solid-state stability (chemical and physical)	Thermal and thermal/humidity solid-state stability (chemical and physical)
Hygroscopicity profile	Equilibrium moisture content and hygroscopicity profile (1)
Particle attributes: size, shape, distribution, surface area	Particle attributes: size, shape, distribution, surface area
Effects of mechanical aggravation and processing	Effects of mechanical aggravation and processing
Crystal packing information (actual or predicted)	Details of excipient manufacture and processing
	Effective pH in water (30)
	Spectroscopic properties
	Age and storage history of excipients (lot specific)