Which of the following refers to physical incompatibility concerns?

Physical incompatibility concerns primarily relate to how different substances interact when mixed together, leading to unwanted reactions that can affect the properties of a compounded sterile preparation. In this context, container reactions encompass the potential for materials from the container or delivery system to leach into the compounded mixture or for the components of the preparation itself to react with the materials of the container.

These interactions are critical to consider as they can alter the stability, efficacy, and safety of the preparation. For instance, certain medications may be chemically reactive with plastics or glass, leading to degradation or precipitation. Understanding these interactions helps maintain the integrity of the compounded sterile preparations, ensuring patient safety and therapeutic effectiveness.

The other choices do not align with physical incompatibility. Molecular changes refer to alterations at the chemical level, therapeutic effects focus on the clinical outcomes of medications, and medication dosages pertain to the amounts given, which are not directly about physical compatibility issues.