SciFinder Scholar: This is a great place to start looking for information about your drug product’s active ingredients, formulation, and excipients because it covers the chemical literature and patent literature. Patents are great sources for information on chemistry as well as manufacturing processes.
US PharmacopeiaGeneral Chapters contain analytical standards, assays and quality control information. Monographs contain Drug "recipes."
FDA Drug Databases: find package inserts and much more