Green’s Dictionary of Slang

(US drugs) of a doctor or dentist, to write prescriptions for narcotics.

1938		D. Maurer ‘Lang. of the Und. Narcotic Addict’ Pt 2 in Lang. Und. (1981).
1959		J.E. Schmidt Narcotics Lingo and Lore 162: Of a dope peddler, to agree to sell to a particular addict.