Pharmacology and mechanism of action

Levamisole is the L-isomer of tetramisole and is more active than the racemic mixture. It was introduced in 1966 as a veterinary drug and a little later as a human anthelminthic drug against ascariasis. The drug has also shown to be effective against hookworms (Ancylostoma duodenale and Necator americanus), but results of reported studies are inconsistent. The mechanism of action of levamisole in helminthiasis is through its stimulation of autonomic ganglia (nicotinic receptors) of the worms. On exposure to the drug, immature and adult worms show spastic contraction followed by tonic paralysis. This mechanism seems to be common to other anthelminthics such as pyrantel and bephenium hydroxynaphthoate. In higher doses, levamisole acts as an immunostimulant. It restores depressed cell-mediated immune mechanisms in peripheral T-lymphocytes, but may have marginal effects in immunologically competent individuals. The clinical implication of this effect in the treatment of helminthiasis is unknown.

Indications

Monoinfections with Ascaris lumbricoides. In polyinfections, mebendazole is the drug of choice.

Side effects

During the treatment of nematode infections the drug produces minor side effects including nausea, vomiting, abdominal pain and headache. During prolonged treatment as an immunomodulator in rheumatic arthritis and in cancer patients, serious side effects such as blood disorders (agranulocytosis, neutropenia and thrombocytopenia), kidney damage, influenza-like reactions, vasculitis, photosensitivity and allergy to the drug have been reported.

Contraindications and precautions

The drug should be avoided in patients allergic to the drug. Administration of levamisole may provoke a reaction similar to that seen after intake of alcohol together with disulfiram. During long-term treatment, patients with kidney damage or with blood disorders may experience exacerbation of their diseases.

Interactions

Levamisole has been reported to displace the protein binding of rifampicin in vitro. The clinical significance of this is as yet unknown.

Originator

Solaskil,Specia,France,1971

Uses

Levamisole is used for initial and secondary immunodeficient conditions, autoimmune diseases, chronic and reoccurring infections, large intestine adenocarcinoma, helmintosis, and rheumatoid arthritis. Synonyms of this drug are decaris, tetramizole, and others.
Levimasole is also a drug of choice for ascardiasis. Numerous investigations show that a single dose of levamisole heals from 90 to 100% of patients with ascardiasis, in particular those infected with A. duodenale. It is less effective against ancylostomiasis and strongyloidiasis. However, it is not effective against N. americanus. It seems likely that it has a gangliostimulating effect on parasite tissues in both the parasympathetic and sympathetic regions. Moreover, it is presumed that this drug has an immunomodulatory effect on the host organism. Synonyms of this drug are decaris, solacil, ergamisol, tramisol, immunol, and others.

Indications

Levamisole (Ergamisol) was originally developed as an antihelminthic drug. It potentiates the stimulatory effects of antigens, mitogens, lymphokines, and chemotactic factors on lymphocytes, granulocytes, and macrophages. It has been shown to increase T cell–mediated immunity.
Levamisole has been used successfully in treating chronic infections. It also has been approved for use in combination with fluorouracil in the treatment of colorectal cancer.

Indications

Levamisole (Ergamisol) is an antiparasitic drug that has been found to enhance T-cell function and cellular immunity. The drug improves survival of patients with resected colorectal cancers when combined with 5-fluorouracil; the mechanism of this interaction is not known. Levamisole does not have antitumor activity against established or metastatic cancer and has not been found useful in the adjuvant therapy of cancers other than colorectal cancer.
The major adverse effects of levamisole are nausea and anorexia. Skin rashes, itching, flulike symptoms, and fevers also have been observed.

Definition

ChEBI: Levamisole is a 6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b][1,3]thiazole that has S configuration. It is used (generally as the monohydrochloride salt) to treat parasitic worm infections in pigs, sheep and cattle and was formerly used in humans as an adjuvant to chemotherapy for the treatment of various cancers. It is also widely used as an adulterant to coccaine. It has a role as an antinematodal drug, an antirheumatic drug, an immunomodulator, an immunological adjuvant and an EC 3.1.3.1 (alkaline phosphatase) inhibitor. It is an enantiomer of a dexamisole.

Therapeutic Function

Antiinflammatory

Antimicrobial activity

Its principal activity is against Asc. lumbricoides and hookworms. Worms are paralyzed and passed out in the feces within a few hours.

Pharmaceutical Applications

The l-isomer of tetramisole, available as the monohydrochloride. The d-isomer has no anthelmintic activity. It is very soluble in water and is stable in the dry state.

Mechanism of action

Levamisole has immunomodulating activity. It is believed that it regulates cellular mechanisms of the immune system, and the mechanism of its action may be associated with activation and proliferative growth of T-lymphocytes, increased numbers of monocytes and activation of macrophages, and also with increased activity and hemotaxis of neutrophylic granulocytes. Levamisole also exhibits anthelmint action. It also increases the body’s overall resistivity and restores altered T-lymphocyte and phagocyte function. It can also fulfill an immunomodulatory function by strengthening the weak reaction of cellular immunity, weakening strong reaction, and having no effect on normal reaction.

Pharmacokinetics

Oral absorption: c. 90%
C_max 150 mg oral: 0.5 mg/L after c. 2 h
Plasma half-life: c. 4 h
Volume of distribution: 100–120 L
Levamisole is rapidly absorbed from the gut and extensively metabolized in the liver. It is excreted chiefly in the urine.

Clinical Use

Ascariasis
Hookworm infection
Levamisole has been used in rheumatoid arthritis and some other conditions that are said to respond to its immunomodulatory activity.

Side effects

Nausea, gastrointestinal upsets and very mild neurological problems have been reported.

Veterinary Drugs and Treatments

Depending on the product licensed, levamisole is indicated for the treatment of many nematodes in cattle, sheep and goats, swine, poultry. In sheep and cattle, levamisole has relatively good activity against abomasal nematodes, small intestinal nematodes (not particularly good against Strongyloides spp.), large intestinal nematodes (not Trichuris spp.), and lungworms. Adult forms of species that are usually covered by levamisole, include: Haemonchus spp., Trichostrongylus spp., Osteragia spp., Cooperia spp., Nematodirus spp., Bunostomum spp., Oesophagostomum spp., Chabertia spp., and Dictyocaulus vivapurus. Levamisole is less effective against the immature forms of these parasites, and is generally ineffective in cattle (but not sheep) against arrested larval forms. Resistance of parasites to levamisole is a growing concern.
In swine, levamisole is indicated for the treatment of Ascaris suum, Oesophagostomum spp., Strongyloides, Stephanurus, and Metastrongylus.
Levamisole has been used in dogs as a microfilaricide to treat Dirofilaria immitis infection in the past, but is rarely used today. It has also garnered some interest as an immunostimulant in the adjunctive therapy of various neoplasms.
Because of its narrow margin for safety and limited efficacy against many equine parasites, levamisole is not generally used in horses as an antiparasitic agent. It has been tried as an immune stimulant, however.