Mountjoy Prison is to get a team of dedicated counsellors to treat the 250 inmates battling heroin addiction in the jail.
Governor John Lonergan said around half the prison population were on a methadone programme. "The figures highlight the volume of people who would be prescribed prescription methadone. The problem is of a massive scale," he said.
And in a bid to to reduce the huge number of addicts four counsellors from Dublin's Merchant Quay are to be brought in to work with the users.
"We have been in touch with Merchants Quay to arrange for three or four drug counsellors for Mountjoy," Mr Lonergan said.
Contracts have been signed and the team is due to begin work in weeks. At present the jail's medical unit is full to capacity with up to 40 inmates being treated for heroin use - some of whom are on a complete detox while others are slowly being weaned off the drug.
Mr Lonergan said the problem of drugs being brought into the prison was as bad as ever with people throwing bags over the walls and he said this would only be solved when Mountjoy closed.
The governor also said staff were dealing with problems from other drugs with vast numbers of inmates regular cannabis users while many use sleeping pills, valium and prescription drugs to get high. And he warned that the problem is far more difficult to deal with than many people believed.