In the United States, Physician Assistants (PAs) are non-physician clinicians licensed to practice medicine with a physician's supervision. This supervision, in most cases, need not be direct or on site and many PAs practice in remote or underserved areas in satellite clinics. PAs can treat patients and, in most states, prescribe medicine, and in some states in the US they carry a DEA number that gives them authority to prescribe controlled medications like narcotics. PAs in surgical practices also serve as first assists in surgery. PAs provide medical services that are reimbursed under Medicare and third party insurances. Physician Assistants and Nurse Practitioners both provide similar services in most states, the major distinction being that nurse practitioners are registered nurses by trade. Both are also known as Advanced Practice Clinicians (APCs) or mid-level practitioners (MLPs).