Which medication requires a filter size of 0.22 microns when given intravenously?

Phenytoin is the medication that requires a filter size of 0.22 microns when given intravenously because it can crystallize and form precipitates in solution. Using a filter helps to ensure that any potential particulate matter, including crystallized drug, is removed from the solution before it is administered to the patient, which minimizes the risk of complications such as phlebitis or embolism. This practice is critical in maintaining the safety and efficacy of intravenous medications, particularly those like phenytoin that have specific compatibility and stability concerns when transitioning from solid to liquid forms.

In evaluating the context of other medications listed, while fentanyl, amiodarone, and carbamazepine have their own specific administration guidelines and considerations, they do not require a filter of the same size due to crystallization risks as seen with phenytoin.