Which is an appropriate measure while preparing medications in a clean room?

When preparing medications in a clean room, frequent handwashing is essential for maintaining a sterile environment. This practice helps to minimize the risk of contamination, which is crucial when working with medications, especially those that are injectable or have a high risk of infection. Regular handwashing not only removes dirt and transient microorganisms but also reinforces the importance of hygiene in a clean room setting.

While wearing an N95 mask is important in certain contexts, such as when there's a risk of airborne pathogens, it doesn't replace the fundamental routine of handwashing in maintaining cleanliness while preparing medications. Additionally, normal clothing does not provide the necessary protection against contamination; appropriate attire such as gowns or scrubs is required in clean rooms. Therefore, handwashing is the most appropriate and critical measure highlighted in this question.