Medsafe has won praise for moving quickly to stop sales of a herbal remedy linked to Covid-19.
The president of Madagascar has claimed extract from Artemisia annua, also known as sweet wormood, a common type of wormwood plant native to temperate Asia, is a treatment for the coronavirus, but the World Health Organisation says there is no evidence for that.
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There are concerns the extract may cause harm to the liver.
Medsafe has classified the Artemisia annua extract as prescription only, so it can no longer be sold over the counter or online.
Medicines New Zealand, which represents pharmaceutical companies, said clinical trials needed to show a medicine was effective and safe.
Its chief executive, Dr Graeme Jarvis, said there were more than 400 vaccines or treatments for Covid-19 being tested worldwide.
"That's not necessarily to discount the current issue around Artemisia ... I do understand the Max Planck institute in Germany is starting to do some clinical trials to look at whether extracts from this particular source do have any effect whatsoever, but it's fairly early days," he said.
It was his understanding that Artemisia was now considered an unapproved medicine in New Zealand.
"That means you'd have to go to a certified or registered medical practitioner [to get it]."
He said the steps taken by MedSafe were responsible in its primary in its role protecting New Zealanders.
But the restricted access may also now mean it could not be sent overseas for sale in other countries, he said.
While there wasn't any evidence it was successful in treating Covid-19, it had been previously used, Jarvis said.
"It's been used for a long time as a Chinese traditional medicine in the past for treating things like fever and malaria, so there's obviously some established utilisation of it in China."