Lacing is the practice of adding hidden substances to drugs without the buyer’s knowledge. It can mean mixing a cheap filler into cocaine to stretch the supply, adding a powerful synthetic opioid to counterfeit pills, or spraying chemicals onto plant material sold as cannabis. The person consuming the drug has no idea what’s actually in it, which is what makes lacing so dangerous.
Why Drugs Get Laced
The primary motive is profit. At every stage between production and street sale, distributors dilute or adulterate drugs to increase the total weight they can sell. Heroin that starts at roughly 80% purity at the wholesale level often drops to around 40% purity by the time it reaches a buyer, with the lost potency replaced by cheap fillers. According to United Nations data, about three quarters of the total value generated in the drug trade comes from these dilutions happening in the destination country.
Some adulterants also enhance or mimic the effects of the original drug at a fraction of the cost. Fentanyl, for instance, is far cheaper to produce per dose than heroin but dramatically more potent, so a small amount mixed into another substance can create a product that “feels” strong to the user while costing the seller very little. Other additives serve purely as bulking agents, adding weight and volume without any psychoactive effect at all.
Fentanyl in Counterfeit Pills
Fentanyl contamination is the most widespread and lethal form of lacing in the United States today. Counterfeit pills designed to look like prescription medications frequently contain fentanyl in unpredictable, sometimes fatal amounts. DEA laboratory testing from late 2024 found that 5 out of every 10 counterfeit pills tested contained a potentially deadly dose. That’s actually an improvement: in 2023, it was 7 out of 10.
The core problem is inconsistency. Two pills from the same batch can contain wildly different amounts of fentanyl because the mixing process in illegal labs is crude. One pill might produce mild effects while the next causes respiratory failure. There is no way to gauge the dose by looking at, smelling, or tasting a pill.
Xylazine: The “Tranq” Adulterant
Xylazine is a veterinary sedative that has become increasingly common as an adulterant, primarily in fentanyl but also in cocaine and heroin. Its appeal to dealers is simple: it’s cheap and not a controlled substance, meaning it carries less legal risk to traffic.
For the person who unknowingly consumes it, xylazine slows breathing, heart rate, and blood pressure to dangerously low levels. It causes extreme sedation that can stop breathing entirely. The most critical detail about xylazine is that naloxone (the standard overdose reversal medication) does not reverse its effects. Naloxone works only on opioid receptors, and xylazine doesn’t act on those receptors. In someone who overdoses on a fentanyl-xylazine mixture, naloxone will reverse the fentanyl component but leave the xylazine sedation and respiratory depression untouched. Public health experts still recommend administering naloxone in these situations because fentanyl is almost always present alongside xylazine, so reversing even part of the overdose can save a life.
Levamisole in Cocaine
Levamisole is a veterinary deworming agent that has been found in a significant portion of the cocaine supply for over a decade. Researchers aren’t entirely sure why it’s so popular as an adulterant, though it may subtly enhance cocaine’s stimulant effects while also adding bulk.
The health consequences are serious. Levamisole attacks white blood cells, sometimes causing a condition called agranulocytosis, where the body’s infection-fighting cells drop to near zero. In one documented case, a 68-year-old man who used cocaine arrived at a hospital with a white blood cell count less than half the normal minimum. His infection-fighting neutrophil count had plummeted to just 40 cells per cubic millimeter, compared to a healthy range in the thousands. His blood counts recovered within four days of stopping cocaine use, which confirmed levamisole as the cause. Beyond blood cell damage, levamisole has been linked to skin inflammation affecting blood vessels and neurological problems.
Laced Cannabis and Synthetic Cannabinoids
Cannabis can be laced with synthetic cannabinoids, chemicals dissolved in a solvent and sprayed onto plant material. These synthetics bind to the same brain receptors as THC but often with much greater strength and faster onset. One of the first identified synthetic cannabinoids, JWH-018, has significantly higher receptor affinity and potency than natural THC.
The symptoms of synthetic cannabinoid exposure go well beyond a typical cannabis high. In a survey of 169 users, about 30% reported headaches, 20% experienced paranoia or panic, and roughly 10% had dizziness or fainting. More alarming effects included racing heart and difficulty breathing (reported by about 6.5%), nausea and vomiting, and in rare cases, seizures and temporary paralysis with complete loss of muscle tone. Severe toxic reactions documented in medical case reports include psychosis, kidney damage, cardiac arrest, dangerously high body temperature, and stroke.
How to Test for Lacing
Fentanyl test strips are the most accessible detection tool currently available. They’re small paper strips that can detect fentanyl and some of its chemical cousins in pills, powders, and injectable drugs. In controlled testing, these strips had a false negative rate of just 3.7%, meaning they correctly identified fentanyl the vast majority of the time. They also successfully detected two common fentanyl analogs, acetyl fentanyl and furanyl fentanyl, in both powder and pill forms.
To use a fentanyl test strip, dissolve at least 10 milligrams of the substance in half a teaspoon of water (use a full teaspoon for methamphetamine, MDMA, or ecstasy). Dip the wavy end of the strip into the water for about 15 seconds, then lay it flat for two to five minutes. A single pink line on the left side means fentanyl was detected. Two lines means it was not detected. A single line on the right side, or no lines at all, means the test failed and you need a new strip.
Test strips have real limitations. They detect fentanyl specifically but not other dangerous adulterants like xylazine, levamisole, or synthetic cannabinoids. A negative fentanyl result does not mean a substance is safe. Additional harm reduction steps include keeping naloxone on hand, avoiding mixing different substances, not using drugs alone, and never assuming a new batch is the same as a previous one, even from the same source.
Why Lacing Is So Hard to Detect Without Testing
Most adulterants are invisible. Fentanyl is active in microgram quantities, amounts too small to see, taste, or smell. Xylazine and levamisole are white powders that blend seamlessly into cocaine or heroin. Synthetic cannabinoids sprayed onto plant material leave no visible trace. The only reliable way to identify these substances is chemical testing, either through test strips, reagent kits, or the drug-checking services that some harm reduction organizations now offer. Visual inspection, smell, and taste tell you essentially nothing about what a substance actually contains.