Dr Pert said Tramadol was a strong painkiller which was addictive, and could cause sleepiness, which made driving and operating machinery dangerous.
"If people want medicine, the best thing is to go to a pharmacist or their doctor.
"There are regulations for a reason and that's to protect safety."
He said people should not have spare antibiotics lying around as they should take the full course prescribed.
"It is fraught with danger."
Pharmacist Ian Edward said he was surprised to find people doing such a thing.
"I just wouldn't have thought that was something that happens."
He said not only was it bad practice, it was also illegal.
"As far as I'm aware it's not legal. Prescription-only medicine can only be obtained by a prescription so they shouldn't be able to do it, full stop."
More than that it was bad practice, Mr Edward said.
He said with medicine like antibiotics there was always the potential for a reaction to happen.
Taking Tramadol when it was not prescribed was "very bad practice not to be recommended at all".
Mr Edward said even when a person was prescribed Tramadol by a doctor, as pharmacists they were very mindful of providing the patient with a lot of information about the possible side-effects.