Epilepsy New Zealand hopes this week's coronial inquest into six unexplained epilepsy deaths changes the way the disorder is treated.
It comes after New Zealand's drug buying agency Pharmac faced criticism for switching the brand of the drug, known as Logem, affecting 11,000 patients.
Chief executive Ross Smith says his organisation and other groups warned Pharmac the plan to change brands was dangerous.
"It's really important for the families, but also for the wider community to know whether the change in brand that Pharmac forced on people had anything to do with their loved ones deaths."
He told Kate Hawkesby people taking medication for epilepsy should never have had their medication switched at the counter.
"It was unacceptable. People with epilepsy should never have been forced to change their drug at the pharmacy counter. That only should have ever taken place with their prescribing doctor, taking into account their circumstances and their seizure history."