who has the authority to legally write a prescription
Medical prescription National or local (i.e. state or provincial) legislation governs who can write a prescription. In the United States, physicians (either M.D., D.O., or D.P.M.) have the broadest prescriptive authority. All 50 states and the District of Columbia allow licensed certified Physician Assistants (PAs) prescription authority (with some states, limitations exist to controlled substances). All 50 states allow registered certified nurse practitioners and other advanced practice registered nurses (such as certified nurse-midwives) prescription power (with some states including limitations to controlled substances).[11][12] Many other healthcare professions also have prescriptive authority related to their area of practice. Veterinarians and dentists have prescribing power in all 50 states and the District of Columbia. Clinical pharmacists are allowed to prescribe in some states through the use of a drug formulary or collaboration agreements. Florida pharmacists can write prescriptions for a limited set of drugs.[13] In all states, optometrists prescribe medications to treat certain eye diseases, and also issue spectacle and contact lens prescriptions for corrective eyewear.[14] Several states have passed RxP legislation, allowing clinical psychologists (PhDs or PsyDs) who are registered as medical psychologists and have also undergone specialized training in script-writing to prescribe drugs to treat emotional and mental disorders. Chiropractors may have the ability to write a prescription, depending on scope of practice laws in a jurisdiction.