Pharmacists will be legally obliged to substitute branded medicines with cheaper, generic drugs within months.
The Irish Medicines Board (IMB) said assessments are under way on the county's top 20 active substances that make up approximately 1,500 individual medicines.
The cholesterol-lowering drug Atorvastatin (Lipitor) will be the first one available under the scheme, by mid August, with two to three following each month after.
IMB chief executive Pat O'Mahony said specialist staff have been preparing for the introduction of the generic substitution legislation in recent months.
"Generic medicines meet exactly the same standards of quality and safety, and have the same effect as the original branded medicines," he said.
The Health (Pricing and Supply of Medical Goods) Act 2013 was signed by President Michael D Higgins last week and is expected to commence later this month when consultations and assessments begin. Under the system, the IMB will publish a list of interchangeable medicines on its website showing those medicines that can be safely substituted by pharmacists.
The first 20 active substances were selected by the Department of Health on the basis of overall cost to patients and the State, which forks out some two billion euro on drugs each year. A Department of Health spokesman said it is not possible to estimate the possible savings from the new legislation.
Meanwhile, an IMB survey found eight out of ten consumers would accept a generic medicine if offered it by their doctor or pharmacist while nine out of ten who previously used generic medicines said they had a positive experience. It also revealed GPs (64%) and pharmacists (31%) are the most trusted sources of medicines advice.
However, it also found one in four people were not familiar with the term 'generic medicine' and that 17% of respondents would not accept a generic if offered it by their healthcare professional.