This marks a significant increase on 1995, when only one in ten drug deaths took place outside Dublin.
A report by the Health Research Board said this reflected a sharp growth in heroin use outside Dublin, jumping by 280% between 1998 and 2002.
"Regional results reflect the trends in treated problem opiate use which is one of the indirect indicators of opiate use in the community," said Dr Jean Long, co-author of the report.
She said heroin-related deaths accounted for the largest proportion of drug-related fatalities.
The report, Drug-related deaths in Ireland 1990-2002, is the first comprehensive review of the problem.
Official recorded figures show a "substantial increase" in drug-related fatalities between 1995 and 2000, from 43 to 119, followed by a sharp decline in 2001, to 88 and a small rise in 2002, to 91.
Outside Dublin, there was a 775% increase in the number of drug deaths, from four in 1995 to 35 in 2002 - a figure that has risen every year.
In Dublin, the number of drug deaths grew by 43% in the same period, from 39 to 56.
Drug-deaths in Dublin peaked at the turn of the decade, to 91 in 1999 and 90 in 2000, before dropping sharply to 55 in 2001 and 56 in 2002.
But the report pointed out that deaths due to the indirect results of drug use were not systematically documented.
It said indirect deaths had only been assessed in small studies in Dublin.
"The findings of the review indicate an underestimate in opiate-related deaths in Dublin and provide little information on deaths as a result of other drugs," said Dr Long, who is a senior researcher in the Drugs Misuse Research Division of the HRB.
She said that was why the National Drugs Strategy had identified the need for precise information on drug-related deaths.
As a result, the HRB was requested last February by the departments of health and justice to develop a National Drug-Related Deaths Index.
The report said a study of Dublin City Coroners Court by Ray Byrne in 2002 found a considerably higher death toll from drugs than recorded by the General Mortality Register, which is the official database.
The Byrne study found that Ballymun, Ballyfermot and the Canal Communities had by far the highest rates of heroin-related deaths in Dublin - and were 16 times greater than localities not designated as drug task force areas.
His study found that the drugs most frequently involved in deaths were benzodiazepine tranquillisers (68%), heroin (62%), methadone (57%) and alcohol (47%).
The Byrne report found that 13% of drug-related deaths occurred in prison or within a short time after release.
Drug-related deaths in Ireland can be viewed at www.hrb.ie.