The legal validity of prescriptions has been extended from six months to 12 months from today.
The change means prescribers can write prescriptions for patients that are valid for up to one year.
From September, patients can also ask their pharmacists to extend prescriptions to a maximum of 12 months, if they have a prescription dated March 1st or later.
The new measures are expected to provide flexibility for patients and reduce demand on primary care services.
It is thought the change could also reduce costs for patients who do not receive free GP care via a GP Visit Card or Medical Card.
Health Minister Stephen Donnelly is encouraging people to talk to their prescribers when their current prescription is due for renewal.
"The changes taking effect today will be welcomed by many patients, particularly those who are stable on medication and who are deemed by their prescriber to be suitable to receive a 12-month prescription, as it reduces the need for repeat visits," he said.
"I'm encouraging people to talk to their GP or other prescriber at their next appointment to see if they are suitable for extended prescriptions.
"Pharmacists also have a very important role to play, and I'm pleased that by giving pharmacists authority to extend prescriptions from six to 12 months, subject to their professional judgement, we are recognising their expertise and their valued contribution to healthcare in Ireland," he added.
The change has been implemented following the Minister's acceptance of a recommendation from the Expert Taskforce to Support the Expansion of the Role of Pharmacists.
It's the first recommendation of the taskforce which was set up last July.
Certain medications will be excluded from prescription extension.