Life-saving drugs can still cost up to 14 times more in the Republic than they do in the North.
A survey by the Irish Independent has shown that there are still huge discrepancies in the price of medicines at different pharmacies -- both inside and outside the State.
Cancer drug Exemestane is the most glaring example as this costs just €6 a month in the North compared with a price tag of up to €86 in the Republic.
As this drug is often prescribed for several years to women who have had breast cancer, the price difference can add up to thousands of euro per patient.
Boots had the highest price tag we found for Exemestane, at €86.30, while Tesco pharmacies charge €81.06.
New pharmacy Healthwave in Dundrum is charging substantially less at €29.95 per month.
However, the drug remains far cheaper across the Border in Newry, where the price is just £5 (€6) for the generic version at McKeevers Chemist.
Manager Adrian Woods said that a cheap generic version of Exemestane had been available in the UK since last year.
"The case of Exemestane is probably one of the largest differences between brand and generic, and you could be talking a saving of nearly €1,000 over the year," he said.
Mr Woods said that the number of customers from the Republic buying medicines had nearly doubled in the last six months since the Irish Independent highlighted savings.
That flood of custom north comes as the latest CSO figures show that prescription drug prices in Ireland rose 7.7pc last year -- nearly 40 times as fast as general inflation.
These spiralling costs came despite attempts by the HSE to cut prices and make it easier to buy generic medicines -- though unfortunately we found there was often little difference in price between the two down south.
However, our survey shows that it is not always cheaper to travel north to buy medicine, as in some cases drugs are cheaper down south, making it vital to check before incurring travel costs.
Some branded medications such as depression medication Cymbalta and heart drugs Rosuvastatin and Exforge were cheaper in all outlets surveyed in the Republic.
New entrant to the Irish pharmacy market Healthwave in Dundrum gained hundreds of customers last week after it slashed prices to patients who sign up for its Healthpass subscription service, which costs €25 a year to join.
Its prices are often a fraction of those in other pharmacies -- for example, Sildenafil -- the generic version of Viagra -- costs €4.95, one-fifth of the €25 price tag in some other chemists.
This is achieved by cutting overheads, making strong use of technology and taking sharply reduced profit margins in the hope of getting a high volume of repeat business and preventing the need to travel north to buy affordable medicine, said its owner Shane O'Sullivan.
Tesco prices also came out cheaper than some of its competitors for many medicines and it said it was opening its sixth pharmacy in Ireland in Gorey, Co Wexford, today.
Boots Ireland said it was "committed to offering affordable medicines to customers and our pricing on prescription medicines is competitive within the Irish marketplace".
The Irish Pharmacy Union, which represents pharmacists, said: "The Irish pharmacy market is one of the most liberal and competitive in all of Europe and competition on pricing is nothing new to Irish pharmacists."
The ongoing rollout of reference pricing by the HSE -- setting maximum prices for specified drugs -- would result in the prices of off-patent and generic medicines falling considerably further, said spokesman Jim Curran.
Aideen Sheehan Consumer Correspondent