Inside a high-security wing at Christchurch Men’s Prison, the intensive supervision unit is for high-risk offenders – those with mental health issues or who arrive high or drunk and are forced into compulsory detox.
They usually sleep it off for several days under 24-hour surveillance.
"They can have the shakes or the sweats," says Principal Corrections Officer Glenys O’Sullivan. "They can also be vomiting or hallucinating."
But the worst drug to deal with is not what you think. It’s not meth, synthetics or Class A drugs, but rather one that’s much more socially acceptable.
"It's probably alcohol," Ms O’Sullivan says. "We've seen a lot of prisoners, they get to the stage they are hallucinating.
"They don’t know where the door is and they think the door is over there and those prisoners sometimes have to go into hospital for hospital treatment. They are that bad."
The latest data from Correction shows 91 per cent of inmates have lifelong mental health issues or substance abuse disorders. And there’s no quick fix, experts say.
"The journey of addiction is long and complicated and complex - because if it was simple and we could flick that switch it would be easy for anyone to change," says Marion Tizzard of Odyssey House Christchurch.
Alcohol and drug rehab has been expanded across prisons, with a focus now on giving prisoners support for a year after release to help them stay clean in the real world, too.