levamisole
Meaning of levamisole: An old deworming drug now met far more often as a cocaine adulterant, capable of wiping out the white cells that fight infection.
Definition of levamisole
Levamisole is an antiparasitic drug that paralyzes intestinal worms, and it also alters the activity of immune cells. It was once given alongside fluorouracil after surgery for colon cancer, and it has been used for a childhood kidney disorder. Human marketing was withdrawn in several countries after it caused a severe fall in white cell counts. Veterinary use continues.
What was it used for in medicine?
Its original job was killing roundworms, which it does by locking open a channel in the worm's muscle so the parasite is paralyzed and expelled. Interest then shifted to its effect on the immune system, and it was combined with fluorouracil as treatment after surgery for colon cancer. That combination was genuinely standard for a period and then abandoned, replaced by regimens that worked better, so describing it as an experimental cancer drug misses the history in both directions. It is still used in some countries as a steroid-sparing agent for a relapsing kidney condition of childhood, and it remains an ordinary antiparasitic in veterinary practice.
Why does it turn up in cocaine?
It is cheap, white, bitter and hard to distinguish from cocaine by look or by simple field testing, and it appears to add to the stimulant effect. A large share of the cocaine supply in several countries has been found to contain it. The result is that people who have never been prescribed the drug are exposed to it repeatedly, often in unknown amounts.
What harm does it cause?
| Effect | What happens |
|---|---|
| Agranulocytosis | Infection-fighting white cells collapse, leaving fever and mouth ulcers |
| Skin vasculitis | Purple net-like patches that die back, typically on the ears, nose and cheeks |
| Autoantibodies | Blood tests turn positive in a pattern mimicking primary vasculitis |
The white cell collapse is the reason the drug left the human market, and it is the reason the same picture is now recognized in people using contaminated cocaine. Counts usually recover once exposure stops, but severe infection during the low period can be fatal.
Also known as
Used in a sentence
The rash and neutropenia were attributed to levamisole exposure through contaminated cocaine.
Good to know
Levamisole causes agranulocytosis and a distinctive net-like skin vasculitis of the ears and face, and because it contaminates much illicit cocaine, that combination is recognized in people with no prescribed exposure to the drug.