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Prison manager Jack Harrison said he had "high hopes" for those prisoners, who began the course in March while a new facility was being completed.
"They were in temporary facilities while the new building was being constructed, but I hope the changes these prisoners have made is permanent."
The programme was vital for rehabilitating prisoners, as addiction was a factor in their crimes, he said.
"The prisoners have to be motivated to make the change or else it's a waste of time and taxpayer money."
As part of the programme, prisoners signed a contract, which included a requirement they stay drug and alcohol free, and would undergo additional drug tests.
"We have high hopes of the prisoners continuing to use the skills and techniques learnt while in the drug treatment unit to help them remain drug free and to help them recognise the trigger points that could cause them to relapse," Mr Harrison said.
Corrections Minister Judith Collins on Thursday opened the new unit at Otago Corrections Facility, the first in the country to offer a short-course programme.
An estimated 180 prisoners would attend the Otago programme each year, which is being run by service provider Care NZ.