Natasha (not her real name) is studying a business-related course and has been off heroin for two years, but she says that when she heard she could no longer get her methadone prescription filled at her local chemist, it was like "hitting rock bottom".
Speaking in Dublin's city centre during the week, she said she had been forced to miss her morning classes and had bought 200mls of methadone for €60 on the black market as an emergency measure to get her through the daytime as she cannot get her regular dose until the late afternoon under the new arrangements.
Otherwise, she says she would be left "dying, sick", unable to function and with nausea and pains in her legs and back making her feel like "death warmed up".
"I don't want to be down here today but I have to be down here because I'm sick," she says. "There are loads of others here who have come to buy off others until they get their dose later."
She said her local chemist had been very good to her since she started having her methadone prescription filled there, but she was shocked when she was told that he was withdrawing from the scheme.
"It really is disgraceful," she says. "People are going to start going back using heroin, it's going to be chaos. I'm okay because I'm stabilised . . . but why do they have to pick on methadone patients? They know they need their methadone."
Another problem for Natasha, who has a job, is the requirement for her to attend Dr Steevens's Hospital, near Heuston Station, to get her methadone. She says she meets people there whom she has not seen in years, some of whom offer her some "gear" (heroin).
"Things are going to get real bad, I'm seeing it already," she says. "I'm carrying around a holy medal saying please God let something happen to stop this."
Outside the Amiens Street clinic in Dublin, one of the HSE's emergency methadone centres, another woman who had just received her weekly dose said it was "very busy" on Thursday.
Clean from heroin for seven years, the 28-year-old - who looks a lot older - suffers from a blood-related disease. As a result, she cannot work but says methadone allows her to function properly.
"For me to get my dose makes me feel normal," she says. "If you go off it, it's like getting hit with a bang off a bus, methadone goes into your bones . . . I don't like the thought of living off a bottle, but it's part of my life now.
"I'd say everyone's going to just turn back to gear. . . people are going up scoring and getting gear."
Another man, who did not want his name to be revealed, told The Irish Times on Wednesday night that he has been off heroin for five years and is attending college. He has been with his girlfriend for the last number of months but has not told her of his addiction and she is unaware of his methadone use.
So far his pharmacist has not pulled out of the scheme, but his GP had told him that this was likely to change if the situation escalated.
His biggest fear was that, if he has to attend a drug treatment centre, he will lose the benefit of confidentiality. No one at his college knows about his past heroin addiction, he added.
A group of other methadone users on Amiens Street outlined their fears about the impact of the dispute between the HSE and the pharmacists.
A woman in her 20s said many users were accustomed to getting their "weekly take-away" from their chemists but were now faced with a "lot of running around.
"You're more likely to go out and get heroin because you're sick," she says. "People don't want to be seen coming to a clinic either, a lot of people's families don't know they're on methadone. My mother said to me, 'I saw you at the clinic, what are you doing there, are you back on methadone?' If you go to a chemist, it's private."
Another one of the group said of methadone: "Before you get it, your legs do be irritating you, but when you get it you relax. A lot of it is psychological, in your head, you know?" he says. "People who are on the chemist [ scheme] are cracking up, they really are."