Pharmac knew for more than two weeks that three deaths had been linked to its epilepsy drug brand switch but didn't tell patients or the public.
The drug buying agency continued with the cost-saving brand switch after being told on 29 October that three deaths had been reported to the Centre for Adverse Reactions Monitoring (CARM) over suspicions they were linked to the change.
Emails released under the Official Information Act also show the Pharmac board alerted Minister of Health David Clark to the deaths on 29 October, under the 'no surprises' policy, but he too said nothing publicly.
The medicines safety watchdog Medsafe also knew but only issued a safety notice on 12 November.
It was not until 15 November that Pharmac backed down on its plan to switch about 11,000 people from the Arrow and Lamictal versions of lamotrigine to the generic form Logem, agreeing to provide funding for most people who applied to stay on their original brand.
That same day, 15 November, a fourth death was reported - although the fatality had actually occurred on 12 August.
The Chief Coroner has since launched a joint inquiry into the four deaths, investigating "whether the change in brand to Logem may have changed the seizure control and whether that contributed to the deaths".
There have now been 148 lamotrogine-related adverse reactions reported to CARM since the brand switch began in May, and 126 of those incidents involved people switching to Logem.
Dellys Brown, whose 27-year-old son Reuben was switching between the Lamictal and Logem brands when he died on 12 October, wanted to know why Pharmac didn't act with more urgency.
"What were they waiting for? Why did it take so long for them to act? Is three deaths not enough?"
She said she was not bitter but was disappointed and saddened by the lack of information on the brand switch and the slow follow-up action from Pharmac.
"The information that we got was an orange sticker on the label [of the medicine box] to say that your medication had been changed."
She said that while Reuben had one or two seizures a month, he was "relatively stable" and seemed to be managing well with his epilepsy, which he'd had since age 12.
Reuben's father found him dead in a paddock on the family property in Ōwaka, a small town in Clutha. He had gone out to put up a fence.
Reuben had lived at home for five years preceding his death, so his mother knew how finely balanced medication needed to be to maintain seizure control in people with epilepsy. "It's a very delicate thing to medicate and to get stability with, so to then turn around and change your medication with absolutely no information or consultation or even permission - I mean where are patients rights in this?"
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Jane Randell*, 23, was also switching between the Lamictal and Logem brands, when she died suddenly on 20 September. Her mother Kate* said Pharmac should have stopped the brand switch on 29 October after finding out about the three deaths, rather than waiting until 15 November.
"Somebody else could have died during that period. They needed to act immediately and the 17 days, to me, sounds like it was 17 days of damage control for them," she said.
"For me, it was shocking to hear that they actually had information. They had data, they knew there had been deaths and yet they stalled and did nothing."
She first spoke to RNZ about her daughter's death last month in the hope publicity would alert others to the potential safety risks of switching brands of epilepsy medicines.
"My whole reasoning behind speaking out, in what is the worst time of my life, having lost my daughter, was to prevent anybody else from dying," she said.
To find out Pharmac had said nothing for several weeks when it knew of the deaths had shocked her, she said.
"It's absolutely gut wrenching for me seeing all the work that so many people are putting in to try and help people and to stay well to stay alive. This is like, you know, a kick in the guts and a shift backwards really."
Epilepsy New Zealand chief executive Ross Smith said he was "staggered" to learn it took so long for Pharmac and MedSafe to act.
"I think people in the epilepsy community will be very angry when they hear that," he said.
MedSafe said while it knew about three deaths on 29 October, it waited until 12 November to issue its safety alert to ensure its information was accurate.
"It was important to take time to seek input from other organisations and update the communication based on this feedback," it said in a statement.
Minister of Health David Clark said his sympathies were with family and friends, but there were long-standing procedures for handling reports of possible harm caused by adverse reactions to medicines, and it was not for ministers to manage those processes or decide when those matters were made public.
The documents released to RNZ under the Official Information Act also shed new light on the significance of four people dying within three months.
Medsafe data shows that in the 27 years between 1992 and the start of Pharmac's brand switch there were just six reported deaths associated with lamotrigine and the last death reported was in 2015.
Over those 27 years there were 162 reports of adverse reactions to lamotrigine - about the same number as have been reported in the seven months since the brand switch began in May.
The documents also shows that an estimated 40 people with epilepsy die from sudden unexplained death in epilepsy patients (SUDEP) each year, and roughly eight of those people would be taking lamotrigine.
Pharmac refused to be interviewed for this story but issued a statement to RNZ confirming it knew of the three deaths by 29 October.
"Pharmac has very limited information about the reported fatalities and we may not know the details, including whether there is any connection with the funded brand change, until after the Coroner's investigations are completed."
Director of Operations Lisa Williams said Pharmac was aware of "a high level of anxiety among people on lamotrigine and their families" after media first reported the three deaths on 12 November.
She said the agency then changed its policy "to make it easier for people on lamotrigine to stay on their current brand if their doctor thinks they should".
Since then, more than 1100 people had applied for funding to switch back to their original brand of lamotrigine and 934 people had been approved. Their applications were taking about five working days to process.
Pharmac stressed that people who had been prescribed Logem should not stop taking it. If they had concerns, they should discuss their options with their doctor. Pharmac would refund GPs for this visit so there would be not charge to the patient.
"For most people taking it, Logem works in the same way as the other two lamotrigine brands. Logem has the same active ingredient and is delivered to the body in the same way," Ms Williams said.
Pharmac said Logem had been approved for use in New Zealand by Medsafe and about 80 million doses were used each year including in Australia, Canada, Germany, UK, Spain, France, and the Netherlands.
* Names have been changed