Ra, Brad and Mark Timms. The family would like to see medicinal marijuana available for Brad who has Batten Disease.

A Timaru mother is calling for medical cannabis to be made available to people, including her son with a fatal disease.

Her call comes in the wake of a Wellington teenager in an induced coma being allowed to receive a cannabidiol (CBD) product from the United States.

Associate Health Minister Peter Dunne approved the one-off use of Elixinol from the United States for Alex Renton.

The 19-year-old Nelson man has been in hospital since early April and remains in "status epilepticus", a kind of prolonged seizure.

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CBD should reduce the seizures and allow them to bring him out of the coma.

Timaru parents Ra and Mark Timms have already lost their daughter Jordyn Rose to Batten Disease and now are watching their son, Brad, succumb to the disease.

They believe his seizures and quality of life would be helped by CBD.

Batten disease is a neurological/storage disorder caused by a faulty enzyme that affects every major organ in the body.

The brain is inflamed and eventually every muscle and function in the affected persons body is unable to operate.

With a one in four chance of being passed on, neither parent knew they carried the gene for Batten Disease.

"My husband's family has the Huntingtons gene and we weren't going to have children because Huntingtons has a one in two chance of being passed on, but we decided to because of new research coming out," Ra said.

Jordyn Rose was diagnosed when she was 13 and died at 19, nearly three years ago.

Brad, now 24, was diagnosed at 16.

"My daughter was on so many pharmaceutical man-made drugs, four of five anti convulsants, plus drugs for secretions, drugs for muscle spasms plus pain stuff and a few others as well," Ra said.

"We didn't know which ones were working, and some drugs were managing the side effects. She would reach a stage of toxicity and I would have to withdraw everything and start again."

Brad, 24, is also on a cocktail of drugs. "His cocktail will only get worse as he progresses."

Ra is in contact with families overseas using CBD to manage the seizures.

"You can't tell me when you have stood over your daughter's bed for 24 hours and she is having constant seizures and her body is twisted in muscle spasms you would not try anything. It hurts like hell to see your child suffer and it stays with you," she said.

"Knowing what we know now and facing going through it a second time, it would be great to have another option. All the research has been done overseas, why reinvent the wheel?

"You only have to look on YouTube, people going from having 100 seizures a day to three a day, that is amazing.

"Also think about the taxes and revenue it would raise, the jobs it would create, the reduction of synthetic (pharmaceutical) drugs that often more drugs need to be taken due to side effects and even the textile industry from the bi- products."

Ra has written letters to politicians including Prime Minister John Key and Health Minister Peter Dunne.

"I fully understand why people are against it, but if it was monitored and legally controlled how could it not be beneficial?" she said.

"I ask them how would they deal with seeing their children in that pain. They have been given great power but with that comes great responsibility. I am not asking them to dish it out willy nilly."

She has resisted procuring her own cannabis oil.

"I know lots of people that would do it, but I can't do it with my son. It needs to be in a controlled situation," she said.

"If something went wrong I would be done for manslaughter."

The new flag campaign leaves the couple cold - "$27 million on a new flag when money needs to be spent on new drug therapies. As a parent you feel so helpless and totally inadequate," Mark said.

The early symptoms of Batten Disease ranged from a loss of vision, behavioural issues, speech problems and learning difficulties.

Prime Minister John Key has said he would not support a parliamentary debate on broadening access to medicinal marijuana because there are alternatives available.

Key said he was he was not "actively looking to progress" a parliamentary debate on medicinal marijuana.