There were 85 fewer deaths from drug poisonings in 2021 compared to the previous year, according to figures from the Health Research Board.
354 drug poisoning deaths were recorded in 2021, compared to 439 in 2020.
The most common drug group reported were opioids, which accounted for seven in ten deaths in 2021.
Using more than one drug was a major factor in the number of drug-related deaths in 2021. The data found eight in ten deaths involved polysubstance use.
Opioids (69%), benzodiazepines (53%), and antidepressants (35%) were the three most common drug groups implicated in poisoning deaths overall.
The majority of deaths involved prescribable drugs, the most common being methadone (129), diazepam (112), alprazolam (107), pregabalin (83), and Zopiclone (59).
Antidepressants were implicated in a greater proportion of deaths among females (47%) than among males (28%).
The most common illicit drugs involved in the deaths were cocaine (107) and heroin (79).
The research found that between 2012 and 2021, the number of deaths involving cocaine more than trebled. These deaths were mostly males and typically due to polysubstance poisonings.
The latest data has also revealed the risks relating to the misuse of prescribable drugs.
In 2021, nine in ten deaths had one or more prescribable drugs implicated and of the top six drugs implicated overall, four of these were prescribable drugs.
One in three drugs involved methadone while one in five involved heroin; these deaths were mostly among males (eight in ten).
Alcohol was implicated in one in three polysubstance poisonings. Opioids were implicated in seven in ten deaths of those who were alone at the time of death.
One in five (18%) of the deceased were known to have ever injected drugs. 23 people (7%) were known to have been injecting at the time of death.
Almost one in two of the deceased had a recorded history of mental health issues, according to the data.
The median age of the deceased was 42.5 years (41 years for males and 47 years for females) - most of whom (77%) were living in stable accommodation.
More than one in ten of the deceased were experiencing homelessness.
Most were residing in the HSE Dublin and North East (28.5%) health region, followed by HSE Dublin and Midlands (23%), and HSE Dublin and South East (18%).
An upward trend in the number of drug poisoning deaths between 2012 to 2021 appeared to plateau in 2019 to 2021 according to the research.
Throughout that time, males have accounted for the majority (six in ten) of drug poisoning deaths every year.
HRB Chief Executive Dr Mairéad O'Driscoll said that while a decrease in the number of drug poisoning deaths recorded in 2021 was welcome, behind each of the numbers was a person, their family and a life lost.
Senior Researcher at the HRB Dr Suzi Lyons pointed out that polysubstance use had increased by 10% since 2012, which "highlights the increased risk of fatal overdose if a person is mixing or using more than one drug".
3,379 poisoning deaths were recorded by the National Drug-Related Deaths Index between 2012 and 2021.
In 2012, the number of deaths from drug poisoning stood at 273.
It rose to 324 in 2013; 311 in 2014 and fell by just one to 310 in 2015.
In 2016, there was another slight decline to 307 before poisoning deaths rose again in 2017 (325) and continued rising (2018 - 361, 2019 - 375, 2020 - 439) until the number of drug poisoning deaths fell to 354 in 2021.
The HRB report has pointed out that that the 17% increase in the number of drug poisoning deaths in 2020 compared to 2019, followed by a decrease of just over 19% in 2021, was a pattern "unlikely to reflect a true change in trend but rather a phenomenon of the Covid-19 pandemic, as was experienced in other countries".
Speaking on RTÉ's Morning Ireland, the Head of Addiction Services at St John of God Hospital in Dublin said there has been a dramatic increase in cocaine use, and in particular crack cocaine, in Ireland.
Professor Colin O'Gara, who is also Clinical Professor of Psychiatry at UCD, said that often cocaine is seen as "harmless" but it can result in cardiac and neurological issues, adding that cocaine is being cut with other substances like fentanyl.
He said the prevalence of synthetic opioids is "frankly terrifying" and said the message around illegal drugs has to change because "you don't really know what you're taking now".
