Inmates in the Dóchas Women’s Prison top the table, consuming almost €1,000 worth of prescribed drugs on average annually.
The prison drug budget is spent on benzodiazepines to treat anxiety and drugs to treat depression, psychosis, HIV, and drug addiction.
Documents seen by the Irish Examiner show the prison pharmaceutical bill increased by 20% in the past six years, to €2.96m in 2010, largely driven by a hike in prison numbers.
Separate data compiled by the Health Research Board (HRB) show high usage of so-called benzos among inmates receiving or seeking drug treatment.
Dr Jean Long of the HRB said most of the benzo use seemed to be prescription- based, rather than illicit, and urged prison authorities to examine this, saying long-term use “compounds addiction”. She called for more investment in psychological therapies.
The HRB figures show that on average, 27% of inmates in treatment were taking benzos. The figure was 39% in Limerick, 44% in Mountjoy, and 54% in Dóchas.
There were also high levels of cannabis use among those in treatment in many prisons, including Mountjoy (38%) and Loughan House open prison (38%).
This is despite the huge investment in drug security in recent years.
Dr Long said there had been a “big improvement” in the reduction of harder drug use, particularly heroin and cocaine, and praised the expansion of methadone treatment.
The pharmaceutical bill rose from €2.4m in 2004 to €2.96m in 2010.
The bill was largely stable between 2004 and 2008, but jumped to €2.8m in 2009 and €2.96m in 2010.
The rise corresponded with a jump in the prison population particularly since 2008, meaning the average cost per inmate in prison fell from €760 in 2004 to €690 in 2010.
A spokesman for the Irish Prison Service said the bill only increased by 4% between 2009 and 2010. He said there were internal procedures and review mechanisms to ensure “safe and effective use of medicine”.
The spokesman said many inmates had complex health needs, including high levels of mental health problems as well as addiction issues.
He said prison policy stated that benzodiazepines should only be used where necessary and for a maximum period of two weeks.
He said “considerable work” had been done in a number of prisons to increase alternative therapies to inmates.
Public health specialist Dr Joe Barry said there was not enough staff to provide psycho-social supports to inmates.
He said the “biggest take-home message” from the figures was to cut the number of people with mental health problems being put in prisons.