Over 300 heroin-users in the Shannonside region were in drug treatment last year.
According to details released under the Freedom of Information Act, they received substitute medication. Almost 8,300 people received opioid-substitution treatment in the first 11 months of last year.
In the vast majority of cases, this is used to treat heroin-addiction. In Ireland, the main treatment for opioid addiction involves methadone and the drug buprenorphine.
In the Longford-Westmeath area, 284 people received opioid substitution prescriptions between last January and November, involving 92 women and 192 men.
That compares to 15 in Roscommon, with four women and 11 men. The total in Sligo-Leitrim was 33, involving 27 men and six women.