Cocaine, heroin, fentanyl… The opioid crisis, which has killed more than 500,000 people over the past 20 years, continues to worsen in the United States. These drugs particularly affect young people and people from humble backgrounds because they are readily available and highly addictive. In particular, fentanyl, which has been wreaking havoc in the United States and Canada in recent years, is about 50 times more potent than heroin, so the risk of addiction and overdose is much higher.
In early 2023, it is xylazine, nicknamed “truck” or “zombie drug”, that is of particular concern to the American Medicines Agency. When combined with other drugs such as opioids or alcohol, its effects are devastating.
Dangerous product often combined with opioids
Xylazine is a compound commonly used in veterinary medicine and approved for use in cats, dogs, and horses as a sedative or prior to anesthesia. Not suitable for humans, this drug is an adrenergic agonist: it blocks the function of adrenergic receptors involved in the regulation of blood pressure or heart rate. By stimulating alpha2-adrenergic receptors, xylazine prevents the release of noradrenaline through alpha1-adrenergic receptors. This leads to slower breathing, lower blood pressure, heart rate and body temperature.
“Once we stop stimulating the alpha1 receptors, we experience loss of consciousness, attention, extreme sedation and possibly delusions or hallucinations: that’s why it’s called a zombie drug, even if the name is rather misleading (…)”, explains Science et Avenir Jean-Paul Tassin, Director Emeritus of Research at INSERM and Specialist in Addictions and Withdrawal Syndrome The term “zombie drug” has in fact already been used to characterize other drugs, such as drugs from the cathinone family, which can cause hallucinations and sedation. In the case of xylazine, this nickname is also justified by the fact that it causes significant skin lesions that can reach necrosis and require amputation of the affected limbs.
Difficult to control traffic
First described in the early 2000s, the number of reported cases of overdose has only increased since the 2010s and more recently since 2020.
Besides the very low price compared to other substances, it is very easy to obtain in the United States. Because it is not intended for human use, it is not as well controlled as other substances such as opioids, which is why the FDA recently took steps to control its entry into the territory. “We recognize the public health implications of xylazine contamination of these illegal drugs and continue to ensure that the legitimate product is for veterinary use only,” Tracey Forfa, director of the FDA’s Center for Veterinary Medicine, said in a press release.
Naloxone is ineffective
“The problem with this drug, and what makes it particularly dangerous, is that the interval between the lethal dose and the effective dose is small,” continues Jean-Paul Tassin. Thus, this substance, taken on its own, is already dangerous in itself, but it is even more dangerous when taken with alcohol or opioids. In the United States, certain drugs, particularly fentanyl, may be diluted with xylazine without notice to consumers. In 2021, more than 90% of drug samples seized in Philadelphia contained xylazine.
This substance is all the more problematic because there is currently no effective treatment to counteract its effects. Naloxone, used as an opioid antagonist, is not effective against xylazine, although its use is still recommended in case of overdose (often due to the combination of xylazine and opioids).