Why Should Some Powdered Medications Not Be Reconstituted Until Just

Why should some powdered medications not be reconstituted until just before administration to the patient?

A) These medications may become inactive or act unpredictably if reconstituted too early.
B) These medications must be semidissolved to be active.
C) It wastes time to prepare a medication too far in advance.
D) The patient must verify the correct reconstitution method.