pharmacologist
A specialist in pharmacology; a researcher or expert in the study of drugs and their effects.
彼は大学で薬学者として新薬の研究をしている。
He is researching new drugs at the university as a pharmacologist.
薬学者 is a pharmaceutical scientist or researcher, whereas 薬剤師 is a practicing, licensed pharmacist who dispenses medicine.
Compound of 薬学 (pharmacology) + 者 (person).