Lethal illicit fentanyl variant discovered in US

US authorities have warned that a powerful analogue of the painkiller fentanyl has been found in illicit drugs seized in some states, including Georgia.

The analogue - called carfentanil - is considerably more potent than fentanyl and can be lethal even in very small quantities, according to the Georgia Bureau of Investigation, which notes it is typically used in veterinary medicine for sedating large animals such as elephants.

Fentanyl has come under the radar of enforcement authorities as it has started to crop up in counterfeit opioid analgesic products and has been linked to dozens of fatalities across North America in the last couple of years.

While carfentanil has so far only been encountered as an illicit drug - often being found in suspected heroin samples - its presence in the marketplace raises real concerns that - as with fentanyl - criminals may end up using it in counterfeit painkillers.

The drug is one of the most potent opioid analgesics ever developed and is around 1,000 times stronger than morphine and 100 times as strong as fentanyl. It is not approved for use in humans.

Carfentanil is "suspected of playing a role in hundreds of overdoses in the Midwest part of the country this past month," according to the GBI, which says it has had to update safety protocols to protect its lab staff from the substance, which can be inhaled or absorbed through the skin and very toxic in small quantities.

Some of the changes include wearing a face mask as well as testing any case suspected to contain heroin under a ventilated hood.