More than 7,600 people received opioid-substitution treatment in the first six months of this year.
In the vast majority of cases, this is used to treat heroin addiction.
In Ireland, the main treatment for opioid addiction involves methadone and the drug buprenorphine.
According to details released under the Freedom of Information Act, 7,645 people received opioid-substitution prescriptions from a community pharmacy in the first six months of this year.
This involved 5,200 men and 2,400 women.
Nearly 4,500 were prescribed by doctors in Dublin, while there were also high numbers in Cork, Limerick and Louth.
There was a 4% increase in the number of people who received opioid-substitution prescriptions last year.
"I would be seeing up to 20 people who have addiction problems, a day," said Dr Austin O'Carroll - a GP in Dublin's inner city.
"And I would see two to three new people a week who are seeking heroin treatment.
"I would also see significant addiction to other drugs, particularly benzodiazepines.
"I would have people coming into me, many of them on up to 30 or 40 tablets a day."
Many people would also be treated in a clinic, such as the National Drug Treatment Centre in Pearse Street in Dublin.
It had a 26% increase in the number treated for heroin addiction last year, with 398 patients seen in 2019.