What constitutes a multi-dose preparation in sterile compounding?

A multi-dose preparation in sterile compounding refers to a medication that can be accessed multiple times from a single container for patient administration. This is defined by the ability to maintain sterility and integrity after the initial opening of the container, allowing for multiple draws and uses.

In the context of the given choices, the correct answer captures this definition by highlighting that a multi-dose preparation is one from which multiple doses can be drawn and used, maintaining the necessary precautions for sterilization and proper handling to ensure patient safety.

The other options do not fit this definition: a single-use vial is intended for only one use, a one-time injection implies that it is administered as a single dose without the capacity for subsequent draws, and dispensing per patient request does not inherently imply that the product is a multi-dose preparation. Therefore, option C accurately reflects the characteristics of multi-dose preparations in sterile compounding.