But there are differences between them and doctors. One distinction: What advanced practice practitioners are permitted by law to do can vary from state to state and even from hospital to hospital. For example, NPs can’t prescribe controlled substances in Florida. In some states, a supervising physician needs to be on site when a PA treats you; in other states, it’s not necessary. Nationwide, an NP’s or PA’s authority to admit you to a hospital is up to the hospital.