The armed robbery took place at Gordons Chemists in Broad Street, Cowdenbeath, Fife, just before 5pm on Friday.
The suspect made off with numerous boxes of prescription medication which officers have warned could be harmful.
Detective Sergeant John Easton, of Dunfermline CID, said: “Thankfully, none of the staff were injured but this was a distressing experience for them and we’re continuing to conduct a number of inquiries locally.
“We’re asking anyone who may have seen this man in the area, or who recognises his description, to contact us as soon as possible.
“The stolen medication can pose a serious risk to a person’s health and should not be taken unless prescribed for you by a medical professional.
“We’re also urging anyone with information about the whereabouts of this medication to come forward immediately.”
The suspect is described as 5ft 8in, in his late 20s or early 30s and of medium build and was quietly spoken with a local accent.
He was wearing a dark grey or black woollen hat pulled over his face with eyeholes cut out, a dark, ribbed, hooded jumper, dark combat-style trousers and dark green or blue trainers with shiny leather on the front.
Anyone with information is asked to contact Police Scotland on 101 or Crimestoppers on 0800 555 111.