<p>This review explores the interactions between packaging materials and pharmaceutical or biological products, emphasizing their critical role in maintaining product quality, stability, and patient safety. The surface characteristics, chemical composition, and physical properties of packaging materials can significantly influence pharmaceutical integrity through mechanisms such as sorption, leaching, additive migration, and material degradation. A comprehensive overview of the major classes of packaging materials is presented, focusing on their compatibility, stability, and impact on the preservation of therapeutic agents. For instance, studies have shown that inadequate packaging protection can reduce the shelf life of certain formulations from nearly six years to only 21 days. Particular attention is given to extractable and leachable compounds that may migrate from packaging components into formulations, their associated risks, and the analytical techniques employed for their detection and quantification. Advances in modern analytical methodologies have greatly improved the sensitivity and precision of assessing these interactions, thereby enabling more accurate evaluation of packaging–product compatibility. Beyond conventional materials, this review also addresses innovative and sustainable packaging solutions, including nanocomposites, biodegradable polymers, and smart systems designed to enhance product protection and functionality. By highlighting the dynamic interplay between packaging systems and sensitive biological environments, this work provides an updated perspective on current challenges and emerging trends in pharmaceutical packaging science. Overall, this review provides practical guidance for formulation scientists and packaging developers in selecting safe, compatible, and sustainable packaging systems for modern therapeutic products.</p>