High Alert say the drug is a pink pill with a "Playboy" logo. It is approximately 1cm long and is also detected as white crystal.
Dimethylpentylone was found in two samples tested by KnowYourStuffNZ in Dunedin.
"High Alert strongly discourages people from taking this substance.
"Testing of any tablets or powder is recommended to help lower the risks."
The person who brought in one of the samples for checking said they had taken the substance and described the experience as "very unenjoyable".
NEW NOTIFICATION ⚠️⚠️ The synthetic cathinone dimethylpentylone has been detected in New Zealand for the first time....
Posted by High Alert on Tuesday, December 7, 2021
"They also experienced a bad comedown, during which they felt anxious."
High Alert said the substance is sometimes called "bath salts" and there is little information on the substance's health risks.
"There is currently no information on the substance's health risks, long-term side effects, or dosage, which makes its use riskier than the use of more common, well-studied substances," the website stated.
There is also limited information about the effects of dimethylpentylone at different dosage levels.
If you have taken the drug, High Alert advises people to not take any more, rest, eat and wait it out.
The website also said people should avoid cannabis, alcohol, caffeine and other substances, and no driving.
"If you are looking after someone who has taken dimethylpentylone, help them to stay calm and remind them they will just have to wait it out."
In October it was announced that festival drug-checking services will get an $800,000 boost from the Government this summer.
Health Minister Andrew Little announced that the funding will be for national co-ordination of services, training of drug-checkers and providing information about the harm that drugs do.
He said the Government was supporting drug-checking services to help keep young people safe at this summer's large festivals and events.
"This is not about condoning drug use, but about keeping people safe," Little said.
"There is clear evidence that having drug-checking services at festivals changes behaviour and reduces harm."
Last summer was the first time that drug-checking services, in which drugs are checked to see if they are what people think they are, were made legal.
Only people who are fully vaccinated against Covid-19 will be allowed to attend events and festivals.
