prescriber

plural prescribers

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.

   2007 May 1, The Associated Press, “Prescription-Writing Law Is Voided”, in New York Times

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.

   2012, Alexander Bergs, Laurel J. Brinton, English Historical Linguistics, volume 1, page 971