Now patient has become excessively drowsy but is responsive to command.Which is next in management?

Patient post laparatomy on patient control analgesia program was being given morphine 1 gm.Now patient has become excessively drowsy but is responsive to command.Which is next in management?

A,Increase oxygen supply by mask
B.Change morphine dose to 0.5 mg
C.Cease patient control analgesia program and give Nurse Supervised subcutaneous Morphine on demand