Levamisole works as a nicotinic acetylcholine receptor agonist that causes continued stimulation of the parasitic worm muscles, leading to paralysis.

[8] Levamisole has gained prominence among aquarists as an effective treatment for Camallanus roundworm infestations in freshwater tropical fish.

[14] Levamisole has been used to treat a variety of dermatologic conditions, including skin infections, leprosy, warts, lichen planus, and aphthous ulcers.

Later papers, from the Janssen group and others, indicate levamisole and its enantiomer, dexamisole, have some mood-elevating or antidepressant properties, although this was never a marketed use of the drug.

[18] It has been used as an adulterant in cocaine, resulting in serious side effects that present as levamisole induced necrosis syndrome, in which erythematous painful papules can appear almost anywhere on skin.

[22][23] Drug testing of racehorse urine has led to the revelation that among levamisole equine metabolites are both pemoline and aminorex, stimulants that are forbidden by racing authorities.

Blood samples following oral administration of levamisole out to 172 hr post-dose did not demonstrate any plasma aminorex levels above that of the limit of quantification (LoQ).

[28] Levamisole may be quantified in blood, plasma, or urine as a diagnostic tool in clinical poisoning situations or to aid in the medicolegal investigation of suspicious deaths involving adulterated street drugs.

[29][30] Levamisole has increasingly been used as a cutting agent in cocaine sold around the globe with the highest incidence being in the United States.

[32] In a series of investigative articles for The Stranger, Brendan Kiley details other rationales for levamisole's rise as an adulterant: possible stimulant effects, a similar appearance to cocaine, and an ability to pass street purity tests.

Evidence from clinical trials support its addition to fluorouracil therapy to benefit patients with colon cancer.

[46] The combination doramectin/levamisole, sold under the brand name Valcor, is indicated for the treatment and control of gastrointestinal roundworms, lungworms, grubs, sucking lice, and mange mites in cattle.