I think of the three you have, clonidine is the biggest one but there are more side effects that go along with it.
Like Nurse Nessa said, there is a risk of rebound hypertension after suddenly discontinuing a continuous dose. So while 1x PRN is not an issue, I wouldn't keep going back to that as my main PRN.
Also clonidine may lower heartrate. Administer judiciously.
Clonidine is centrally acting so this would be great if your patient appears to be in emotional distress and it can also substitute for the lorazepam that others suggested for possible withdrawal. If your patient is not stressed out, beware of the centrally-induced side effects (drowsiness, dizziness) by implementing fall precautions. If you're on night shift, it will certainly help your patients sleep