PHARMACIST Peadar McGovern owns a chemist just North of the Border. He says customers from the republic account for a "sizeable" proportion of his business.
Some even come from as far away as Kerry to stock up on cheaper medications.
Situated in the village of Derrylin, Co Fermanagh, McGovern's Chemist is on one of the main routes from the south to Co Donegal.
It benefits from plentiful passing trade, as well as regular customers living in counties Cavan and Longford.
"We have a lot of customers from just the other side of the Border, from Longford, even people from Kerry," explained Mr McGovern.
"We are on the main corridor from the south to Donegal so quite often we have people who drop off on spec to price medicines and check the differentials.
"It's a phenomenon we've seen over the last four or five years, but it's stronger now than ever, particularly in the last two years," he added.
Mr McGovern is conscious of the effect the movement of customers northwards is having on his colleagues in the republic and said it was "not easy" for pharmacists just south of the Border to keep their business going and employ staff.
"It would have a negative effect for them, but it's a business at the end of the day and I can't refuse business," he said.
The most popular medications for southern customers are cholesterol- lowering statins, blood- pressure tablets and aspirin.
"If pricing was closer, I would have fewer customers coming up. But you have to take account of the exchange rate, too," he pointed out.
He declined to put a figure on the proportion of his customers who are from the south, but Mr McGovern said it was "sizeable".
And while residents in the North enjoy lower prices for medications, they save on the double as they don't have to pay prescription charges like customers from the south have to.