inpatient and outpatient

No, it is not. It is a noun (person admitted to a hospital or clinic), which can be a noun adjunct in terms such as inpatient entrance.

The word "inpatient" is a noun that means a patient who resides in hospital while under treatment. The word "inpatient" can be hyphenated as "in-patient" to avoid confusion with the adjective "impatient". However, the word "inpatient" has three syllables and does not need a hyphen.

probation

Inpatient treatment varies in quality, just as outpatient does. The advantage to inpatient is that you are relieved of the stresses of everyday life, and the staff and counselors have an opportunity to get to know you better so that they can better assess and help you.