prescriber

noun

1. A person who prescribes medication (usually a physician, physician assistant, or nurse practitioner).

   “[…] the law made New Hampshire the first state to try to block pharmaceutical companies’ hard-sell pitches by restricting access to data that identifies doctors and other prescribers.”

2. One who directs or orders, as for example one who makes prescriptive demands on others' use of language.

   “Alongside Webster's dictionary stood a slew of rabid reformers and prescribers of correct English.”