What are the selection criteria for selecting an excipient for a pharmaceutical formulation?

When selecting an excipient for a pharmaceutical formulation, key criteria include compatibility with the active pharmaceutical ingredient (API), stability under storage conditions, and the desired release characteristics of the drug. Additionally, the excipient should be non-toxic, have appropriate regulatory approval, and meet the necessary quality standards for the intended dosage form. Factors such as cost, availability, and ease of manufacturing processes also play a significant role in the selection process.