Pharmakon was a Droid belonging to Esmeraude which appeared in episode 78. She created medicine that contained Dark Power to "cure" the virus that had infected everyone other than Minako.

Pharmakon took the form of a human nurse, but when she revealed her Droid identity, she had a metallic body with a syringe and a scalpel instead of arms. She pinned Sailor Venus to the wall after shooting a volley of syringes, but was destroyed after the Sailor Senshi and Tuxedo Mask came to rescue her.

(Source: Project WikiMoon)