Patients hoping to avail of the Spinal Muscular Atrophy drug Spinraza have been told that it is likely there will be further discussions about funding the drug in the coming weeks.

The HSE informed patients last week that it would not sanction use of the drug because of the cost involved.

The Head of the National Centre for Pharmacoeconomics (NCPE), Professor Michael Barry said he understood that there was probably dismay and disbelief among patients about the Health Service Executive's decision not to fund the drug, but he said "it is not a final no" and that the "door is always open".

Speaking to RTÉ News, Prof Barry said the decision not to fund Spinraza had been made because it "comes at a really high cost" of over half a million euro per patient in the first year and a quarter of a million thereafter, with an estimated cost of €38m over a five-year period.

He said while the drug had been shown to work in clinical trials, the numbers were small and the drug does not cure the condition but can improve well-being.

Professor Barry said it had happened before that companies had come back and looked again at pricing and he anticipates there will be further discussions with the manufacturer Biogen in the near future.

He also said that it was "not surprising" that the HSE had almost exhausted its funding for new drugs for 2019 just eight weeks into the year.

He said that there had been 18 approvals for new drugs and three for drugs already licenced at a cost of €150m over the next five years.

Professor Barry said there is a finite budget but that decision makers were always free to allocate more money to the drug sector. However, he said that money had to come from somewhere.

He would not comment on the possibility that the overspend on the National Children's Hospital might have an impact on this but said "if you overspend in one area it might not be available for another".