Epilepsy New Zealand is raising concerns about Pharmac changing its funding to just a single brand of Lamotrigine epilepsy medication.
About 12,500 people take some brand of Lamotrigine, for either epilepsy or a mental health condition like bipolar.
From 1 May, everyone using Lamictal and Arrow-Lamotrigine brands of lamotrigine 25, 50 or 100 milligram dispersible tablets will need to transition to the Logem brand to keep accessing funding.
After a five-month transition period, Logem will be the only brand funded by Pharmac.
Wendy Nossiter, who has been seizure-free for five years, will start paying extra for her soon-to-be-unsubsidised medication, because she doesn't want to change.
"I've come such a long way in five years, due to my seizures I've developed anxiety and depression, I've struggled a lot with that and to go backwards would absolutely devastate me," she said.
She said it was not really in her budget to pay extra, but it was worth it for peace of mind.
Epilepsy New Zealand was one of the organisations that submitted on the changes and its CEO, Graeme Ambler, questioned the possible implications.
"To go through a change is a big upheaval for people, so if it does initiate a seizure it has a huge impact on their life.
"New Zealand Transport Agency as an example will remove the drivers licence for 12 months after a seizure, so that can impact employment and isolation," he said.
Graeme Ambler said there have been a few cases of people struggling with the medication change.
"Those symptoms range from headaches, psychological issues, feeling down and a change in seizure activity. So we're concerned [about if] those people are looked after and are able to cope with change with minimal impact," he said.
Epilepsy New Zealand was working with Pharmac to ensure the change happens smoothly and anyone affected is properly supported.
Pharmac's chief executive, Lisa Williams, said Pharmac had learnt from previous brand changes and that they needed to enable people to stay on their current brand, if that what was best for them.
"People who have experienced problems changing, their doctors can make an application on an easy form to Pharmac so that we can assess whether or not ongoing funding of the previous brand should be made available.
"We can also accept applications for people where their GPs think it's not going to be possible for them to change," she said.
Ms Williams says people shouldn't notice any difference from the change, which was supported by recent data on Lamotrigine use.
"Our data from 2018, shows that of all the people that were using Lamotrigine in that year, 50 percent of them changed brands during that year and we're not aware of, nor have we been informed of, any significant clinical impact for those people that changed brands," she said.
She stressed the importance of those taking Lamotrigine to continue to do so, unless advised otherwise by their doctor.