Levamisole
Levamisole is an imidazothiazole anthelmintic used primarily against susceptible gastrointestinal nematodes and lungworms in livestock. It also has a history of microfilaricidal and empirical immunomodulatory use in small animals. Its established antiparasitic role is distinct from proposed immune effects, for which clinical efficacy evidence is much less developed.
Group
Imidazothiazole anthelmintic
Mechanism of Action
Levamisole activates nicotinic acetylcholine receptors at nematode neuromuscular junctions. Sustained depolarization produces spastic paralysis, allowing susceptible worms to be expelled or eliminated. Proposed immunomodulatory actions include effects on lymphocyte and phagocyte function, but the molecular basis and contribution to clinical benefit in veterinary disease are incompletely established.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Endoparasites | 5–8 mg/kg | PO | Once | |
| Endoparasites | 10 mg/kg | PO | Every 24 h | Up to 2 days; Separate two-day alternative. |
| Hookworms | 10 mg/kg | PO | Every 24 h | Up to 2 days |
| Historical microfilaricide | 10 mg/kg | PO | Every 24 h | Up to 10 days; Course 6-10 days; macrocyclic lactones are preferred. |
| Immunostimulant | Reference only | PO | 0.5-2 mg/kg three times weekly; efficacy is not established and the weekly pattern is not a single repeating hour interval. | |
| Chronic pyoderma immune adjunct | 2.2 mg/kg | PO | Every 48 h | With appropriate antimicrobial treatment; benefit is uncertain. |
| Historical SLE immune adjunct | 3–7 mg/kg | PO | Every 48 h | Up to 120 days; Historical alternative alone or with corticosteroids; assess clinical benefit. |
| Capillaria lungworm | 7–12 mg/kg | PO | Every 24 h | Up to 7 days; Course 3-7 days. |
| Filaroides osleri infection | 7–12 mg/kg | PO | Every 24 h | Up to 45 days; Course 20-45 days. |
| Alternative lungworm treatment | Reference only | PO | 7.5 mg/kg twice daily or 25 mg/kg every other day for 10 days; confirm parasite diagnosis. The Angiostrongylus 7.5 then 10 mg/kg staged regimen lacks a route, as does the 8 mg/kg Crenosoma entry. | |
| Capillaria aerophilia | 10 mg/kg | PO | Every 24 h | Up to 5 days; Five-day course, repeated after 9 days without treatment. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Endoparasites | 4.4 mg/kg | PO | Once | |
| Lungworms | 20–40 mg/kg | PO | Every 48 h | Five treatments only. |
| Capillaria aerophilia | 10 mg/kg | PO | Every 24 h | Up to 5 days; Five-day course, repeated after 9 days without treatment. |
| Ollulanus tricuspis | 5 mg/kg | SC | ||
| Plasma-cell gingivitis immune adjunct | 25 mg/animal | PO | Every 48 h | Three doses only; efficacy unestablished. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 8 mg/kg | PO | Once | |
| Nematodes | 8 mg/kg | SC | Once | Inject in the midneck; use a product with a verified active-equivalent concentration. |
| Dictyocaulus infection | 5.5–11 mg/kg | PO | ||
| Dictyocaulus infection | 3.3–8 mg/kg | SC | ||
| Nematodes | 7.5 mg/kg | PO | Once |
Sheep
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 8 mg/kg | PO | Once | |
| Nematodes | 7.5 mg/kg | PO | Once |
Pigs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | Reference only | PO | 8 mg/kg in drinking water. Intake and treatment period must be established for the particular flock/herd water-medication protocol. |
Rabbits
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Gastric nematodes | 12.5–20 mg/kg | PO | ||
| Extragastric nematodes | 12.5–20 mg/kg | SC |
Goats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 7.5 mg/kg | PO | Once |
Llamas
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 5–8 mg/kg | PO, SC, IM | Once |
Reptiles
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 5–10 mg/kg | PO | Every 336 h | Initial dose and one repeat; fecal exam 14 days after second treatment, with a third only if still positive. |
Birds
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Nematodes | 4–8 mg/kg | IM, SC | Every 240–336 h | Repeat once after 10-14 days; can cause vomiting, ataxia or death. Avoid IM where possible and do not use in debilitated birds. |
| Capillaria infection | 15–30 mg/kg | PO | Every 240–336 h | Oral/crop bolus then repeat after 10-14 days; water-medication alternatives depend on intake. |
| Poultry nematodes | 18–36 mg/kg | PO | ||
| Ratite Libyastrongylus control | Reference only | PO | 30 mg/kg at one month of age, monthly for seven treatments, then four times yearly; an IM alternative is also described. Requires a calendar and bird-specific risk assessment. |
Indications
- Treatment of susceptible gastrointestinal nematodes and lungworms in cattle, sheep, goats or pigs with a corresponding veterinary product.
- Treatment of selected susceptible nematode infections in poultry or other veterinary species with a supported regimen.
- Treatment of selected lungworm infections in dogs and cats, including some Capillaria or Aelurostrongylus infections, with limited species- and parasite-specific clinical evidence.
- Historical reduction of circulating Dirofilaria immitis microfilariae in dogs.
- Historical adjunctive immunomodulation for selected canine chronic pyoderma or feline plasma-cell gingivitis cases, with unproven clinical benefit.
Contraindications
- High microfilarial burden can produce reactions after parasite killing.
- Severe debilitation or major renal/hepatic impairment; avoid routine use in stressed cattle immediately after vaccination, dehorning or castration. FIV/FIP cats have additional cited concerns; benefit in FeLV is unproven.
Interactions
- Avoid pyrantel because additive neuromuscular toxicity is possible.
Adverse effects
- Cholinergic toxicity, vomiting and injection-site swelling
Toxicity
Excess exposure can cause cholinergic signs and neuromuscular dysfunction; stop treatment and provide supportive care.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Levamisole 50 mg tablet | Tablet | 50 mg / tablet | PO |
| Levamisole 184 mg bolus | Tablet | 184 mg / tablet | PO |
| Levamisole 2.19 g bolus | Tablet | 2.19 g / tablet | PO |
Monitoring and Administration
Check microfilaria status before relevant canine treatment.
Use a clean needle and injection site for each animal.
Levamisole may yield aminorex in horses, relevant to performance restrictions.
Hydrochloride and phosphate preparations have different salt identities; retain the stated active-equivalent strength before substitution.
Levamisole phosphate injections are listed at 136.5 and 182 mg/mL without a clear active-equivalent basis. These are not treated as hydrochloride/base concentrations. Powder packets are listed without enough carrier composition to infer mg/g.
Additional feline lungworm protocols include 20-40 mg/kg PO every other day for 5-6 treatments and staged Aelurostrongylus courses of 15, 30 then 60 mg/kg with nonuniform spacing; retain treatment count and tolerance monitoring. Capillaria alternatives use 4.4 mg/kg SC for 2 days, 8.8 mg/kg two weeks later, or 5 mg/kg PO for 5 days followed by 9 days off, repeated twice. These must not be flattened into one wide range.
Equine immunomodulation alternatives include 2.2 mg/kg PO daily for 3 days then 4 days off, for 4-6 weeks; EPM adjunct 1-2 mg/kg/day PO. A 2.5 mg/kg weekly injection entry lacks its route. Bird regimens include 13.65% phosphate injectable product 5-15 mL/gallon water for 1-3 days, repeated after 10 days, and a nebulized 1 mL in 15 mL saline; exposure and phosphate-equivalent basis require a product-specific plan. Avoid dehydration caused by withholding water.