Technically, as long as you have your DEA, you can write for what ever class drug you were approved for. Legally, there should be a valid reason for RXing the drug.
I mostly RX antibiotics, pain meds for dental procedures, but I have given Valium for anxious patients, muscle relax for tmj, steroids for severe inflamation, antihistamine allegics reactions. and all that fun stuff. All ofthe above did coincide with my treatement.