Levamisole — what it is and why you should care

Ever heard the name levamisole and wondered what it actually does? It started as an anti-parasitic medicine but has a messy history in human use. Today you’re most likely to see it in veterinary medicine, or sadly, as a dangerous contaminant in street drugs. Knowing the basics can protect your health.

Uses and how it works

Levamisole kills certain worms and affects the immune system. Doctors once used it in people to treat worm infections and even as an immune booster in cancer treatment years ago. Over time, safety problems pushed many countries to stop using it in humans. Veterinarians still use it for livestock and pets when needed.

If someone prescribes levamisole, follow their instructions exactly. Don’t try to dose yourself based on internet posts. The correct dose depends on the problem being treated, and only a medical professional should decide that.

Major risks and what to watch for

The biggest danger with levamisole is severe drops in white blood cells, called agranulocytosis or neutropenia. That leaves people open to bad infections. Signs include fever, sore throat, mouth sores, unexplained bruises, or sudden infections. If any of these show up after taking levamisole — or after using cocaine, which is sometimes cut with levamisole — get medical help right away.

Levamisole can also cause skin problems. Some people develop painful, purplish skin sores or areas of skin that die off. Those symptoms often need urgent care from a doctor or a dermatologist.

Besides these severe effects, levamisole may cause more common side effects like nausea, headache, or dizziness. Mixing it with other drugs that weaken the immune system raises risk. Pregnant or breastfeeding people should avoid it unless a doctor says otherwise.

One extra red flag: levamisole shows up in illegal drug supplies. Tests of seized cocaine often find levamisole mixed in. Users who experience fever, weakness, or infections after using street drugs should tell medical staff about possible levamisole exposure — it changes how doctors check and treat you.

Want practical steps? If you’re prescribed levamisole, ask your provider about blood tests and how often to check counts. If you or someone you know uses street drugs, consider testing services and seek help if you see worrying symptoms. And if you’re treating animals, follow veterinary guidance and safety rules for handling and dosing.

Have questions about antiparasitic medicines or drug safety? Our site covers related meds and safety tips. Look up articles on antiparasitics and contact a healthcare professional for personal advice — nothing here replaces medical care tailored to you.