Officials have compiled an updated report on Scotland's naloxone programme, which hands out kits of the drug to the family, friends or carers of heroin addicts.
It found that 5.5% of all opioid-related deaths in Scotland in 2012 occurred within four weeks of prison release.
This was down from the 8.4% recorded the year before and a baseline figure of almost 10% for the period from 2006-10. The drop was described as "encouraging" by officials but they stressed that the fall could not necessarily be linked to the naloxone programme because other factors may be at work.
Scotland was the first country in the world to announce it was setting up such a scheme in November 2010, with thousands of naloxone kits distributed since then.
The drug can save comatose heroin addicts with a single injection, with the special kits given to the family, friends or carers of addicts, as long as consent is given by the person who is deemed to be at risk.
The latest official figures, published by ISD Scotland, show that the number of drug overdose prevention kits issued in 2012-13 rose by more than 10%.
The programme gave out 3,833 take-home naloxone kits that year, compared with 3,458 kits in 2011-12. A total of 1,461 take-home kits were issued by prisons in Scotland in 2011-12 and 2012-13. They are given to people at risk of opioid overdose and are supplied to people when they are freed from jail.
Looking at deaths among newly-released prisoners, the report concluded: "While encouraging, this decrease cannot necessarily be causally linked to the national naloxone programme and may partly reflect patterns of declining opioid use in Scotland, particularly among younger people."
Community safety minister Roseanna Cunningham said: "The programme is an important intervention which, delivered alongside resuscitation training, is helping to save lives."