Emergency services callouts to incidents linked to synthetic drugs have tripled in Auckland in recent months.
Figures released to Newshub show recently there's been a spike of up to 30 incidents a week - many involving multiple patients.
Medical director Dr Tony Smith says it's hard to put a figure on the number of callouts.
"We've had approximately 400 this year, and in recent weeks we've seen a particular spike when we have seen up to 30 incidents a week."
St John responded to 121 synthetic drug-related incidents in April - twice the number it attended in March.
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Dr Smith says many patients have life-threatening reactions.
"Patients become unconscious; they have very poor breathing, and as they gain consciousness it's common for them to become very confused, agitated and often violent."
In the past year more than 25 people have died in Auckland from synthetic drugs.
The drugs are used across a wide spectrum of people of all ages, says Dr Smith. He says there have been deaths in recent years that can't yet be proven to be related to synthetic drugs.