Pharmacists will be legally obliged to substitute branded medicines with cheaper, generic drugs within months.
The Irish Medicines Board (IMB) said assessments are underway 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.
Pat O'Mahony, IMB chief executive, 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.
Former Late Late Show host Gay Byrne is among those involved in a campaign to promote the use of generic medicines for understandgeneric.ie.
He said they "are approved in exactly the same way as all other medicines, guaranteeing that generics meet the required safety and quality standards".
"With generics, the name, packet or colour of your medication may change, but what's inside is essentially the same, only more affordable," he added.
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 €2bn on drugs each year.