The death of a fifth person whose epilepsy medicine was changed has renewed calls for an inquiry into Pharmac's decision to make the switch.
The death of an Auckland man in his 30s just before Christmas was linked to a change in his epilepsy drugs just weeks before his death.
Pharmac changed to a generic form of epilepsy drug lamotrigine, called Logem, in October. Since then five deaths have been reported to the Centre for Adverse Reactions Monitoring as possibly linked to the change.
The National Party is calling for a ministerial inquiry into the change, and the head of Epilepsy New Zealand Ross Smith agrees.
"The epilepsy community has been saying this right from the start, that they shouldn't be mucking around with the brand changes, so we've basically said it's time to call time on this brand-switch - enough is enough."
He said a ministerial inquiry could answer questions about why Pharmac initially ignored warnings from Medsafe that the change was not a good idea.
"Overseas lamotrigine is one of those drugs where any changes in brands should only be done in conjunction with the person's primary care physician or prescribing physician.
"That's not what happened in New Zealand. As we know people were rocking up to the pharmacy and being told at the pharmacy counter - your medication is changing. It's not international best practice and it's not how people on lamotrigine should be treated."
National Party health spokesperson Michael Woodhouse said five deaths suggested lives were being put at risk by the change.
A joint coronial inquiry will be held into the deaths, but Woodhouse said a ministerial inquiry would have additional benefits.
"I think there is a greater level of urgency about this," Woodhouse said.
"A ministerial inquiry can have terms of reference that are very very broad, and can also work on a time frame that would give us the answer to that key question of whether there is a causal link between the drug switch and the deaths, much sooner perhaps than a coronial inquiry could."
In a statement, a spokesperson for the government said the deaths were being investigated by the coroner, and in the meantime Pharmac had made changes to the way the brand was being managed.
The spokesperson said there were procedures for handling reports of possible harm caused by adverse reactions to medicines, and they should be left to clinical experts, not Government ministers.