I have just read the Rev Commissions Leaflet on claiming medical expenses (IT6) and it does not specify that the medical expenses must have been incured in Ireland.
The point about the health care only being available outside Ireland is only mentioned
in relation to travel expenses, not the medical expenses.
I did a search on this site, and Clubman says that he successfully claimed for expenses incured abroad.
I assume you have receipts for all expenses.