Several drugs can make people appear zombie-like, but the one most commonly associated with the term today is xylazine, a veterinary tranquilizer known on the street as “tranq.” When mixed with fentanyl, it leaves people slumped over in a near-catatonic state, sometimes for hours, often with severe skin wounds that have earned the combination the name “zombie drug.” Other substances produce different versions of zombie-like behavior, from the frenzied aggression caused by flakka to the tissue destruction linked to krokodil.
Xylazine: The Drug Behind “Tranq”
Xylazine is an animal sedative never approved for human use. It works by blocking the release of norepinephrine, a chemical your nervous system uses to keep you alert and responsive. Without it, heart rate drops, blood pressure falls, muscles go slack, and consciousness fades. The result is a person who appears frozen in place, bent over or collapsed, barely responsive to the world around them. This deep sedation can last far longer than a typical opioid high, sometimes extending for hours.
What makes xylazine especially dangerous is that it now shows up in a large share of the street drug supply. In 2024, 36 percent of fentanyl powder samples seized in the U.S. contained xylazine. The combination is particularly lethal because fentanyl already suppresses breathing, and xylazine pushes that suppression further. Between January 2019 and June 2022, fentanyl-involved overdose deaths where xylazine was also detected increased by 276 percent across monitored jurisdictions.
The skin damage is what truly sets xylazine apart. Chronic use causes blood vessels to constrict by activating receptors in vascular smooth muscle, starving nearby tissue of oxygen. This leads to dark, rotting ulcers that can appear anywhere on the body, not just at injection sites. Because xylazine also lowers blood pressure and slows the heart, the body’s ability to heal these wounds drops dramatically, and secondary infections often set in. In severe cases, limbs require amputation.
Why Naloxone Alone Won’t Work
Naloxone (Narcan) reverses opioid overdoses by knocking opioids off their receptors in the brain. Xylazine is not an opioid. It acts on a completely different set of receptors, which means naloxone does nothing to counteract its effects on breathing and sedation. Because xylazine is almost always mixed with fentanyl, naloxone should still be given during a suspected overdose to address the opioid component. But the person may remain unresponsive even after receiving it.
The CDC recommends calling 911 and providing rescue breaths if someone appears to be overdosing on a xylazine-fentanyl combination. Rescue breathing is especially important because xylazine’s suppression of breathing can persist long after naloxone has reversed the fentanyl. First responders are now trained to suspect xylazine involvement when naloxone fails to restore normal breathing.
Flakka: Zombie-Like Aggression
If xylazine creates the slow, slumped zombie, flakka creates the fast, violent one. Flakka (alpha-PVP) is a synthetic stimulant that floods the brain with dopamine, producing a state called agitated delirium. People in this state can become extremely agitated, confused, and violent. Body temperature spikes dangerously high, the heart races, pupils dilate, and some users display what bystanders describe as superhuman strength, likely because the drug suppresses the normal pain signals that would limit exertion.
Alpha-PVP triggers a surge of physical activity that comes on faster and harder than methamphetamine. The bizarre, erratic behavior that follows has been captured in countless viral videos, particularly from Florida around 2015, where users were seen running through streets naked, attacking objects and people, or collapsing in public. Seizures are a real risk. The combination of extreme overheating, cardiac stress, and violent muscle activity can be fatal.
Krokodil: Tissue Destruction From the Inside
Krokodil is the street name for homemade desomorphine, an opioid cooked from codeine tablets using household chemicals. The drug itself produces a heroin-like sedation, but it’s the manufacturing byproducts that cause the horrifying tissue damage associated with it. The final product often contains hydrochloric acid, red phosphorus from matchbook striker strips, iodine, gasoline, and paint thinner.
When injected, these contaminants attack the body from the injection site outward. Gasoline and hydrochloric acid cause discolored, scaly skin and open ulcers. Iodine damages muscle and the endocrine system. Red phosphorus eats into cartilage and bone. The skin around injection sites turns greenish and scaly (hence “krokodil,” from the Russian word for crocodile) before dying and sloughing off. In advanced cases, bare bone becomes visible through the wounds. The drug became widespread in Russia in the 2000s and has appeared sporadically in other countries since.
Scopolamine: Chemical Submission
Scopolamine, sometimes called “devil’s breath,” produces a different kind of zombie state: one where the person appears awake and functional but has no free will or memory. It blocks acetylcholine, a neurotransmitter essential for memory formation and cognitive function. At high doses, it causes heavy sedation, disorientation, and a blank suggestibility that criminals in parts of South America have reportedly exploited to rob or assault victims. People under its influence may follow instructions, hand over valuables, or walk to ATMs without later remembering any of it.
The drug also causes dry mouth, dilated pupils, and at very high doses, restlessness or hallucinations. Stories of scopolamine being blown into someone’s face as a powder are common in media, though the pharmacology makes that particular method less reliable than dissolving it into a drink. Regardless of delivery, the amnesia it produces is its most distinctive feature. Victims typically wake up hours later with no recollection of what happened.
How These Drugs Disrupt Movement
The shuffling, bent-over posture that people associate with “zombie” behavior comes down to disruption of the basal ganglia, a cluster of brain structures responsible for coordinating voluntary movement. Dopamine receptors (D1, D2, and D3) are the primary controllers of locomotion in this area. Drugs that block these receptors produce symptoms nearly identical to Parkinson’s disease: stiff muscles, slow movement, tremors, and an unsteady, shuffling gait. Drugs that overstimulate them, like flakka, produce the opposite extreme of uncontrolled, jerky hyperactivity.
Sedatives like xylazine and opioids add another layer by activating the brain’s inhibitory pathways, essentially turning down the volume on every signal the brain sends to the muscles. The result is a person who can barely stand, can’t speak clearly, and may not respond to pain. Combined with the muscle relaxation xylazine specifically causes, users can end up frozen in unnatural positions for extended periods, compounding the blood flow problems that lead to skin damage.
Recognizing Different Types of Intoxication
The physical signs vary depending on which type of drug is involved. Opioid intoxication typically presents with pinpoint pupils, slurred speech, drowsiness, and decreased consciousness. Stimulant intoxication looks almost opposite: dilated pupils, rapid heartbeat, sweating, agitation, and sometimes chest pain or convulsions. Sedative intoxication from drugs like benzodiazepines causes unsteady walking, slurred speech, low body temperature, and low blood pressure.
Xylazine-fentanyl intoxication combines features of both opioid and sedative overdose, with the added sign of skin wounds that don’t heal. The presence of dark, necrotic ulcers on someone who also shows signs of opioid use is a strong indicator of xylazine exposure. Needle track marks, unusual odors, and pupil size all provide clues, but polysubstance use is increasingly common, making any single set of signs unreliable on its own.