What Is Levamisole in Cocaine, and Should You Be Worried?

Levamisole is a veterinary deworming drug that is now the most common adulterant in the cocaine supply, and in a small subset of users it can wipe out the white blood cells that fight infection, a condition called agranulocytosis that can be fatal. US Drug Enforcement Administration testing has found levamisole in roughly 70% to 80% of seized cocaine (PMID 22677078). Most people who use contaminated cocaine never develop a serious problem, but the ones who do can become dangerously ill, and the early signs (fever, mouth sores, infections that won’t clear) are easy to dismiss. You cannot taste, see, or feel levamisole, and no street-level test can rule it out.

Quick answers

What is levamisole? A drug used to deworm livestock. It was pulled from human medicine in the US in 2000 over side effects. It is now the dominant cocaine cutting agent worldwide.

Why is levamisole in cocaine? It adds weight cheaply, looks like cocaine, and appears to mildly potentiate cocaine’s effects by acting on the same dopamine and acetylcholine pathways, so it stretches product without obviously degrading the high.

Is levamisole in cocaine dangerous? For most people, exposure causes no obvious harm. But in a subset, it triggers agranulocytosis (loss of infection-fighting white cells) or a skin vasculitis that causes purple, necrotic patches. Both can be serious or fatal.

Can you test cocaine for levamisole? Reagent tests can sometimes flag it, but no field test reliably rules it out, and fentanyl test strips do not detect it. Treat any cocaine as potentially adulterated.

What are the warning signs? High fever, sore throat, mouth or anal ulcers, swollen glands, and infections that don’t resolve. Purple blotches on the ears, nose, or limbs point to the vasculitis form. Any of these after cocaine use is a medical emergency.

How common is it, really?

This is not a rare contaminant. DEA surveillance has consistently found levamisole in the large majority of US cocaine, with estimates ranging from about 69% in 2009 to more than 80% in later sampling (PMID 22677078). If you use cocaine in the United States, the statistical default is that your supply contains it. The same pattern shows up in cocaine seized across Canada and Europe.

The reason it is so widespread comes down to economics and chemistry. Levamisole is cheap, white, and crystalline, so it passes a visual inspection. It survives the conversion to crack. And unlike inert fillers such as baking soda or sugars, it is pharmacologically active in a way that seems to complement cocaine rather than dilute the experience, which makes adulterated product harder for users to detect by feel.

Why a dewormer hurts some people and not others

Levamisole’s dangerous effect is immune-mediated, which is why it strikes unpredictably. It is not a simple dose-poison relationship where more always means worse. Instead, in susceptible people, levamisole (or a reactive metabolite it forms in the body) prompts the immune system to produce antibodies that attack the person’s own neutrophils, the white blood cells that are the front line against bacterial infection (PMID 22393119).

When neutrophils are destroyed faster than the bone marrow can replace them, the count can crash toward zero. That state is agranulocytosis, and it leaves the body unable to contain infections that a healthy immune system would clear without notice. A minor throat infection can become life-threatening sepsis. Published case series put the share of levamisole-exposed patients who form these anti-neutrophil antibodies somewhere between roughly 0.4% and 20%, and the risk appears higher in women (PMID 22677078). A confirmed case in Journal of Medical Toxicology documented agranulocytosis directly tied to levamisole-contaminated cocaine after other causes were excluded (PMID 20358411).

The same immune mechanism drives the second classic presentation: levamisole-induced vasculitis, an inflammation of small blood vessels that produces tender purple patches, often on the ears, nose, cheeks, and extremities, sometimes progressing to skin death (necrosis). These lesions are a visible red flag that the immune system is reacting to the adulterant.

Because the reaction depends on individual immune response rather than dose, you cannot “use a little to be safe.” Someone can use contaminated cocaine for months without a problem and then react, and there is no test that predicts who is susceptible.

Warning signs you should not ignore

Get medical care if any of these appear after using cocaine, even if you feel otherwise fine. Agranulocytosis is silent until an infection takes hold, and by then time matters.

• Persistent high fever or shaking chills
• Sore throat, mouth ulcers, or anal/genital ulcers that appear or worsen suddenly
• Swollen lymph nodes
• Any infection that won’t clear, or that comes back fast
• Painful purple or black patches on the skin, classically the ears, nose, and limbs
• Unusual fatigue or feeling profoundly unwell after recent use

Tell the clinician that you have used cocaine. This is the single most useful thing you can do. Levamisole toxicity is diagnosed with a simple blood count (a CBC showing low neutrophils), but only if the doctor knows to look. Treatment, stopping exposure, antibiotics for infection, and sometimes a drug called G-CSF to restart white cell production, works far better when started early. Good Samaritan laws in most US states protect people who seek medical care for drug-related problems.

Reducing the risk

There is no way to make levamisole-contaminated cocaine safe, but you can lower your exposure and catch problems sooner:

• Test your supply. Reagent kits can identify whether a sample is actually cocaine and can sometimes flag adulterants. They will not quantify levamisole, but they are still the baseline harm reduction step, and the same testing routine lets you screen for fentanyl, which is a separate and more immediate lethal risk.
• Use fentanyl test strips every time. They do not detect levamisole, but fentanyl contamination of cocaine is a leading cause of stimulant overdose deaths, and strips are cheap insurance. See our walkthrough on how to use fentanyl test strips.
• Track your own baseline. If you develop recurrent infections, mouth sores, or unexplained fevers, raise levamisole with your doctor directly.
• Don’t share equipment. A suppressed immune system plus shared straws or pipes is a fast route to transmissible infection.

DanceSafe sells reagent test kits and fentanyl test strips that cover cocaine screening.

The bottom line

Levamisole is in most of the US cocaine supply, you cannot detect it by sight or feel, and in a vulnerable minority it can destroy the immune system’s infection-fighting cells. The overall odds of serious harm per use are low, but the consequences when it happens are severe, and the early warning signs are easy to miss. If you use cocaine and develop a stubborn fever, mouth ulcers, or purple skin patches, treat it as an emergency and tell the doctor about the cocaine.

For the full picture on testing, cardiovascular risk, and safer-use protocols, see our cocaine harm reduction guide. To check how cocaine interacts with alcohol and other substances, use our interaction checker, and our breakdown of cocaine and alcohol covers why that specific combination is so hard on the heart.

Sources: PMID 22677078 | PMID 22393119 | PMID 20358411