Larissa Wright knew her addiction had hit rock bottom when she woke up and couldn't move her hands or legs.
"I was thinking, 'I'm never going to be able walk again,'" she told Newstalk ZB's Chris Lynch.
She had been taking nitrous oxide, known as NOS, for at least four months by then, huffing up to 160 canisters a day at her addiction's peak.
"I was going through a really hard time, so I used to have the NOS to make me feel better," she said.
"It used to make me feel good about myself, make me feel relaxed... but then you'd get this feeling, where it would be like 'nang, nang, nang, nang', it sort of pounds, and things around you would be distorted."
She was always chasing that feeling, her habit snowballing until it cost $380 a day to maintain.
And then she woke up one morning and couldn't move.
"I had to have intensive care, paramedics and an ambulance come and transport me to hospital... I couldn't move my hands, my legs, everything was numb."
She's mobile with a walker now - but needs help with daily activities, like showering.
And now she's sober, she wants people to know how addictive - and easily available - the drug is.
Selling nitrous oxide, or laughing gas, for therapeutic use is banned under the Medicines Act - and it requires a prescription to buy.
But it's still legally available to buy in food products and is often used in whipped cream canisters.
High doses of the drug give a short-lived, euphoric spike.
A surge in online sales of NOS prompted a Medsafe investigation last year, and a warning for retailers to only sell products that weren't regarded as prescription medicines.
Wright warns the addictive gas is still within easy reach, especially in Christchurch, where she lives.
"As an experiment, I sent in a 16-year-old into a local dairy on the east side of Christchurch and they walked out with a 50 pack, or $80 worth, no questions asked."
She says there need to be tougher regulations, and more education, around NOS.
Wright now lives with life-long injuries, and while she doesn't think she'll ever fully recover from her addiction, she's found solace, through counselling.
She credits the drug and alcohol counselling at He Waka Tapu, a Wainoni-based kaupapa Māori service, for her recovery.
"You don't have to pay anything, you can literally do a self-referral, right on the spot," she said.
"You can just walk in there, they'll treat you like whānau," she said.
Medsafe's group manager, Chris James, says the agency's probe into the illegal supply of nitrous oxide is ongoing.
"Medsafe strongly advises that it should not be used for recreational purposes.
"This would not only be illegal and leave the user open to prosecution under the Medicines Act 1981, but there are dangers associated with its use."
That danger's amplified when NOS is taken with other illicit drugs, and can muddle a user's concentration, he says.
"As a gas, it can also have serious physical effects on the lungs and mouth. Long-term use may lead to various medical issues."
James says the gas has been classified as a therapeutic substance because it's used under strict supervision in a healthcare setting - and because of the risk it poses when it's taken recreationally.
And while food products, like whipped cream, contain nitrous oxide, selling it for anything else crosses the line.
"If it is being sold for a purpose that involves inhalation, then that sale would be illegal."
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