Which of the following is most likely to be used as a substitute if the non-formulary drug is escitalopram?

Cabergoline is a dopamine agonist primarily used to treat conditions related to hyperprolactinemia and Parkinson's disease. It does not share the same mechanism of action as escitalopram, making it an inappropriate substitute for treating mood disorders or anxiety.

Ciprofloxacin is an antibiotic used to treat bacterial infections. It has no relation to the treatment of mood disorders or anxiety, and therefore, it cannot serve as a substitute for escitalopram, which targets neurotransmitter systems.

Amantadine is primarily used to treat Parkinson's disease and certain viral infections. While it has some effects on neurotransmitters, it is not classified as an SSRI and does not function in the same way as escitalopram. Thus, it is not an appropriate substitute for managing depression or anxiety.