For 11 years, Jacinta Newport's daughter has been in pain.

Sometimes in the hips, sometimes in her lower limbs, that pain, along with frequent visits to specialists, has been a constant, just like her cocktail of medicines and often terrible side effects.

"It's just affected her life on every level," Mrs Newport says.

Her daughter, now 22, was diagnosed with juvenile arthritis when she was 11. The condition affects about one in 1000 New Zealand children.

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"We've tried everything. We've been everywhere. We know what works and what doesn't work."

Mrs Newport, a nurse, said her daughter had worked hard to complete her education and lead a social life, despite side-effects from opioid medicines including drowsiness, fatigue, dry mouth, blurred vision and hyperalgesia, or heightened sensitivity to pain.

The family have spent the best part of two years working to get a Sativex prescription.

The cannabinoid spray was used to treat spasticity due to multiple sclerosis but was also prescribed for people with a range of pain conditions.

Pharmac, the agency responsible for deciding which medicines get subsidised, plans to discuss Sativex with its primary clinical advisory committee this month, a first step towards possibly more public funding.

Currently 27 New Zealanders were approved to use the spray.

Ms Newport said many more people could benefit from the spray, and those who already accessed it could barely afford it, and often had to endure a ridiculous ordeal beforehand.

She believed passionate emotions about cannabis-based medications had muddied the debate.

Even predatory criminals complicate discussion of Sativex, with some people with the spray reluctant to reveal their identities for fear of being burgled. She wanted her daughter, currently prescribed opiates, to not be named for the same reason.

Ms Newport said some specialists had not properly understood the depression they cited as a reason for not prescribing Sativex to her daughter.

"Why they won't do it is because she's had a bit of depression, but the drugs cause the depression. And this is the problem...they use it as an excuse."

She believed some parents of epileptic children were breaking the law, or even moving to Colorado, to access medical marijuana and treat chronic pain their loved ones suffered from.

The US state has been at the vanguard of cannabis legalisation and medicinal marijuana regulation.

Mrs Newport and her daughter have even travelled to Sydney Children's Hospital for a pain management programme.

The nurse asked why her daughter still couldn't get Sativex when she believed it was more widely-prescribed or accessible in some other countries.

"She would love to be on Sativex, to give it a go. She's not a recreational marijuana user."

One man who shattered his knee in a 2012 accident and had a chronic pain condition said he went through hell before getting Sativex, which now made his condition more tolerable.

He said the condition was like "taking a blowtorch to your skin or cutting a finger off with no anaesthetic."

He wanted to remain anonymous, concerned his access to opiates and Sativex would attract thieves.

He said he tried 16 different medicines, including opiates, tricyclics and gabapentin.

"They all had horrible side effects. Methadone gave me mood swings, depression and rage, opiates turned me into a zombie," he said.

"It was a dark time. I am lucky to be here."

Eventually a doctor prescribed him Sativex -- but he said ACC would not initially fund it.

He said the agency was later ordered to fund his Sativex but he was restricted to 12 sprays a day.

Yet he said Sativex was overpriced here and he was not allowed proper dosing for his condition.

He said public agencies should fund a generic brand, made in New Zealand, to make Sativex more accessible and affordable. Currently, innovation in the development and awareness of medical cannabis here was hamstrung.

He said lack of education about Sativex was a problem, and some doctors did not know how to get it, or that it was even an option for people suffering from a range of painful conditions.

Sativex should not be the "last resort" it currently was, he said.

He said Sativex helped him sleep, stopped his nausea, relaxed him, increased his appetite and had saved him from the "depression rollercoaster" his previous prescription caused.

Better still, he said the cannabis-based medicine, unlike opiates, had no "toxic dose" and he did not build a tolerance.

Leading neuropathic pain and cannabinoid experts here said Sativex could probably help some people, but was unlikely to be a panacea.

University of Auckland cannabinoid expert Associate Professor Michelle Glass said clinical data suggested Sativex had side effects no worse than those of opiates.

"But I suspect the cost and the challenges associated with getting it would probably put a lot of specialists off going through that process," she said.

"The suggestions are that, for otherwise intractable pain, it's definitely an option. A lot of the existing medicines are generally considered to be more effective, but for those who don't respond, there's certainly a sub-population that does respond to this."

Associate Prof Glass said Pharmac's fixed budget meant a public subsidy for Sativex would cause other medicines to miss out.

She said Pharmac did a mostly good job of advancing a "reasonably accessible health care model" but there'd always be people who felt they weren't getting access to what they wanted.

"They're tasked with trying to do the best they can for the most people. And with that is always going to come decisions that aren't popular."

She expected interest and innovation in medicinal cannabis to surge in years ahead.

"Everybody's watching with interest what happens in Colorado," she said. "I think the medicinal cannabis field is continuing to grow. There'll be more and more alternatives...emerging over the next few years. I suspect that if things are proven to be useful and valuable in patients, then they will become available through Pharmac."

Earlier this year, 19-year-old Alex Renton's family campaigned for him to be given Elixinol, a cannabidiol made from hemp. Mr Renton's case fired up discussion -- but Prof Glass and others discussing Sativex said mis-reporting of what Elixinol was muddied a debate already prone to misinformation.

University of Otago endocannabinoid researcher Dr John Ashton said studies indicated Sativex could help some people suffering from pain. But he said it was important to take into account individual medical histories and "subtleties" between patients.

"There does seem to be some evidence that it was helping, particularly with people who weren't responsive to other drugs. So the evidence is yes, it has a moderate benefit in some people -- not dramatic, it doesn't take people's pain away -- maybe a 30 per cent improvement, up to 50 [per cent] which I suppose if you're in pain, that might go from being unbearable to liveable."

Dr Ashton said there was concern about the impacts of THC on adolescent development so few people would be happy prescribing Sativex to a child.

He said it was a different situation for a 21 year-old.

Dr Ashton said studies on the impact of Sativex on diabetics with neuropathic pain showed the spray was moderately effective in treating their pain.

A Ministry of Health spokesman said applications to prescribe Sativex were received from specialists, or GPs with a recommendation from a specialist, on a "reasonably regular basis".

There were currently 27 approvals in effect for Sativex and to date there'd been 81 ministerial approvals in total.

These figures were up from 18 months ago, when just four people have an active prescription for Sativex and there'd only been 48 ministerial approvals.

Medsafe said Sativex could be given to people who hadn't responded adequately to other anti-spasticity medication and who showed improvement in spasticity-related symptoms during an initial trial of therapy.