What is the purpose of using a filter needle in sterile compounding?

The use of a filter needle in sterile compounding primarily serves to prevent contamination. Filter needles are designed with a filter that traps any particulate matter, such as rubber, glass, or other contaminants that may be introduced during the process of drawing up a medication from a vial or ampule. This is particularly important in sterile compounding, where maintaining the integrity of the sterile environment is crucial to ensure patient safety and the effectiveness of compounded preparations.

While the other answer choices do reflect important aspects of compounding techniques, they do not specifically relate to the unique function of a filter needle. For instance, a filter needle does not primarily assist in drawing up viscous solutions, nor is its purpose to avoid the formation of air bubbles, though it may incidentally help with these issues. Measuring precise volumes is also not the role of a filter needle, as that would typically involve using calibrated syringes instead. Thus, the key function of a filter needle lies in its ability to help keep compounded products safe from harmful contaminants.