A dangerous animal tranquilizer that can kill humans has become the latest ‘zombie’ drug to run rampant in the US. 

Officials are warning that medetomidine, a powerful drug used for sedation and pain relief in dogs and cats, is being mixed with fentanyl and other opioids and sold in multiple states. 

The drug is not intended for human use and can cause changes to a person’s mental state – making them extremely sedated or ‘zombified.’

It can also slow the heart rate to the point that the organ is unable to pump enough blood to the body, resulting in heart failure, sudden cardiac arrest or death. 

The Philadelphia Medical Examiner’s Office identified the first-ever case of medetomidine intake in the Pennsylvania drug supply in May 2024. 

By the end of the year, officials found 46 people who had died from fatal drug overdoses over the year had consumed medetomidine.

And experts are warning it has now made its way into three-quarters of the illicit drug supply.  

Dr Michael Lynch, an emergency medicine doctor at University of Pittsburgh Medical Center, said: ‘We know it’s probably in about half to three-quarters of our drug supply.

‘[It can] depress your breathing a little bit, lowers your heart rate, and, to a lesser degree, can lower your blood pressure. And it can last for several hours where people are very, very sleepy. 

Officials are warning that medetomidine, a drug used for sedation and pain relief in pet dogs and cats, is being mixed with fentanyl and other opioids and sold in multiple states. (file photo)

He told CBS: ‘It is so different and so severe and progresses so rapidly and doesn’t respond to the usual treatments that we use for withdrawal from different substances like alcohol or opioids or benzodiazepines.’

Medetomidine was also detected in several seized drug samples across Maryland in July 2022, suggesting the drug is spreading. 

The recommended dose of medetomidine for dogs is 750 micrograms and less than 20 mg for cats given through an IV drip. 

Despite not being intended for use in humans, there is another form of medetomidine, sold under brand names Dexdor and Precedex, that is used for sedation and muscle relaxation in people. 

It remains unclear how much of medetomidine can be lethal to human life. 

Medetomidine is often cut with other drugs like fentanyl because when mixed with opioids and other substances, it greatly increases the sedative effects of each drug, which people may perceive as a better or stronger product.

The sedative has most frequently been observed in samples containing fentanyl and xylazine, but the drug has also been identified together with heroin and cocaine, the Center for Forensic Science Research and Education said.

In addition to dropping the heart rate dangerously low, it can cause serious effects such as hallucinations and last longer than other illicit substances it is mixed with.

The drug, which is estimated to be 200 times more powerful than xylazine, also slows neurological functions in the body, resulting in confusion and lethargy, as well as symptoms of opioid overdose like shallow breathing and small pupils.

The drug is not intended for long-term human use and can make dangerous changes to heart rate and mental state – leaving patients in a state of extreme sleepiness.

Pictured: People, some with drug dependency issues sit along a sidewalk in Philadelphia, Pennsylvania

Some medetomidine overdose symptoms include uncontrollable vomiting, excessive sweating, life-threatening levels of blood pressure, fluctuating mental state, tremors and a heart rate over 100 beats a minute. 

The Pennsylvania Department of Health has asked healthcare providers to use naloxone, usually used to treat opioids as treatment against medetomidine overdose – despite the latter drug not being an opioid. 

The medication works by attaching itself to medetomidine receptors and reverses and blocks the effects of it by neutralizing it. 

It can quickly restore normal breathing if it has slowed or stopped due to an overdose and help the body return to its a normal state. 

Dr Raagini Jawa, infectious disease and addiction medicine physician at UPMC told the Post Gazette: ‘Naloxone is still the first-line agent for overdose reversal. 

‘We really need to educate people about rescue breathing and making sure we’re protecting their airways and calling for help, so that if they need oxygen, emergency services can provide supplemental oxygen support for them.’