Levamisole
Levamisole hydrochloride / Levamisole phosphate
Antiparasitic (Antinematodal) / Immune StimulantPOSCIMTopicalDogsCatsSmall MammalsBirdsReptilesHorsesCattleSwineSheepGoats
Also known as: Levasole · Amtech · Ascaridil · Decaris · Ergamisol · Immunol · Ketrax · Meglum · Prohibit · Solaskil · Vermisol · Vizole · cloridrato de levamizol · ICI-59623 · levamisoli hydrochloridum · NSC-177023 · R-12564 · RP-20605 · l-tetramisole hydrochloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
2.2 mg/kg PO every other day, with appropriate antimicrobial therapyPO· q48h
— 🐕
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For recurrent cutaneous infections (immune stimulant) | 2.2 mg/kg PO every other day, with appropriate antimicrobial therapy | PO | q48h | — | 🌎 NA |
| As an immune stimulant | 0.5-2 mg/kg PO 3 times a week | PO | 3 times a week | — | 🌎 NA |
| For adjunctive therapy in dogs with chronic pyoderma | 0.5-1.5 mg/kg PO 2-3 times a week | PO | 2-3 times a week | — | 🌎 NA |
| For adjunctive therapy in dogs with chronic pyoderma | 2.2 mg/kg PO every other day | PO | q48h | — | 🌎 NA |
| As an alternative treatment for SLE | 3-7 mg/kg PO every other day for 4 months; alone or in combination with corticosteroids | PO | q48h | 4 months | 🌎 NA |
| As a microfilaricide | 11 mg/kg PO for 6-12 days. Examine for microfilaria within 7-10 days and at weekly intervals until eliminated or treatment is halted. | PO | q24h | 6-12 days | 🌎 NA |
| For treatment of Angiostrongylus vasorum | 7.5 mg/kg (route not specified) for two consecutive days, followed by 10 mg/kg for 2 days; if the infection is not cleared, the regimen is repeated. | Not specified | q24h | 4 days | 🌎 NA |
| For Crenosoma vulpis (lungworms) | 8 mg/kg once | PO | Once | 1 dose | 🌎 NA |
| For Capillaria (lungworms) | 7-12 mg/kg once daily PO for 3-7 days | PO | q24h | 3-7 days | 🌎 NA |
| For Filaroides osleri (lungworms) | 7-12 mg/kg once daily PO for 20-45 days | PO | q24h | 20-45 days | 🌎 NA |
| For Filaroides osleri (lungworms) | 7.5 mg/kg PO twice daily or 25 mg/kg PO every other day for 10 days | PO | q12h or q48h | 10 days | 🌎 NA |
| For Capillaria aerophilia (lungworms) | 10 mg/kg PO once daily for 5 days; repeat in 9 days | PO | q24h | 5 days | 🌎 NA |
- For adjunctive therapy in dogs with chronic pyoderma: Efficacy not established
- For adjunctive therapy in dogs with chronic pyoderma: May only be efficacious in 10% of cases
- As a microfilaricide: Rarely recommended today. Retching and vomiting are common. Avoid giving on an empty stomach or immediately after drinking water. A 'conditioning' dose of 5 mg/kg PO once a day may be necessary. Stop therapy if abnormal behavior or ataxia develops.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For the treatment of lungworms | 20-40 mg/kg PO every other day for 5-6 treatments | PO | q48h | 5-6 treatments | 🌎 NA |
| For Aelurostrongylus abstrusus (lungworms) | 100 mg PO daily every other day for 5 treatments; give atropine (0.5 mg SC, 15 minutes before administering); or 15 mg/kg PO every other day for 3 treatments, then 3 days later: 30 mg/kg PO, then 2 days later: 60 mg/kg. | PO | Varies | Varies | 🌎 NA |
| For Capillaria aerophilia (lungworms) | 4.4 mg/kg SC for 2 days, then 8.8 mg/kg once 2 weeks later; or 5 mg/kg PO once daily for 5 days, followed by 9 days of no therapy, repeat two times | SC/PO | Varies | Varies | 🌎 NA |
| For the treatment of lungworms | 25 mg/kg every other day for 10-14 days | PO | q48h | 10-14 days | 🌎 NA |
| For Capillaria aerophilia (lungworms) | 10 mg/kg PO once daily for 5 days; repeat in 9 days | PO | q24h | 5 days | 🌎 NA |
| For treatment of Ollulanus tricuspis | 5 mg/kg SC | SC | Once | 1 dose | 🌎 NA |
| As a microfilaricide | 10 mg/kg PO for 7 days | PO | q24h | 7 days | 🌎 NA |
| For adjunctive therapy of feline plasma-cell gingivitis/pharyngitis (immune-stimulant) | 25 mg PO every other day for 3 doses | PO | q48h | 3 doses | 🌎 NA |
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For nematodes in Rabbits | 12.5-20 mg/kg PO (for gastric nematodes) or SC (for extragastric nematodes) | PO/SC | Once | — | 🌎 NA |
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For intestinal nematodes | 5-15 mL/gallon of drinking water for 1-3 days; repeat in 10 days. If birds refuse to drink, withhold water prior to treating. | PO | Daily | 1-3 days | 🌎 NA |
| For gavage in Australian Parakeets (or desert species that refuse to drink water) | 15 mg/kg; repeat in 10 days | PO | Once | — | 🌎 NA |
| For parenteral use | 4-8 mg/kg IM or SC; repeat in 10-14 days. | IM/SC | Once | — | 🌎 NA |
| For immunostimulation | 0.3 mL/gallon of water for several weeks | PO | Continuous | Several weeks | 🌎 NA |
| As a parenteral immunostimulant | 2 mg/kg IM or SC. 3 doses at 14 day intervals | IM/SC | q14d | 3 doses | 🌎 NA |
| As a nebulized immunostimulant | 1 mL (of 13.65% levamisole phosphate) in 15 mL saline | Inhalation | — | — | 🌎 NA |
| For Capillaria infections | 15-30 mg/kg orally as a single bolus or through a crop tube; or 2.25 mg/gallon of drinking water for 4-5 days. Repeat treatment in 10-14 days. | PO | Varies | 1 or 4-5 days | 🌎 NA |
| Poultry nematodes | 18-36 mg/kg, PO | PO | Once | — | 🌎 NA |
| For Libyastrongylus douglassi in Ratites | Give 30 mg/kg PO or IM at one month of age, then once a month for 7 treatments, then 4 times yearly | PO/IM | Monthly then quarterly | Ongoing | 🌎 NA |
- For intestinal nematodes: Using 13.65% injectable
- For gavage in Australian Parakeets (or desert species that refuse to drink water): Using 13.65% injectable
- For parenteral use: Using 13.65% injectable. May cause vomiting, ataxia, or death. Do not use in debilitated birds.
- For immunostimulation: Using 13.65% injectable
- As a parenteral immunostimulant: Using 13.65% injectable
Reptiles
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an anthelmintic (Nematodes, Acanthocephalans, or Pentastomes) | Nematodes: 5-10 mg/kg PO; repeat in two weeks followed by a fecal exam 14 days after the second dose. If positive, a third dose is given. Acanthocephalans, or Pentastomes: as above, but may also be given SC or ICe. | PO/SC/ICe | q14d | 2-3 doses | 🌎 NA |
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an immunostimulant | Dosages have ranged from 2.5 mg/kg injected at 7 day intervals, and 2.2 mg/kg PO every 24 hours for 3 days, then off for 4 days for a period of 4-6 weeks. | Injection/PO | Varies | 4-6 weeks | 🌎 NA |
| As adjunctive therapy for EPM | 1-2 mg/kg per day PO | PO | q24h | — | 🌎 NA |
- As an immunostimulant: Anecdotal reports of beneficial effects in the treatment of nasal viral papillomas, COPD, and EPM have been suggested.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For removal of mature and immature Dictyocaulus vivapurus | 5.5-11 mg/kg PO, either given in feed or as a drench or oral bolus. May also be administered SC at 3.3-8 mg/kg. | PO/SC | Once | — | 🌎 NA |
| For treatment of susceptible nematodes | 7.5 mg/kg PO | PO | Once | — | 🌎 NA |
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For removal of mature and immature Metastrongylus | 8 mg/kg PO in feed or water | PO | Once | — | 🌎 NA |
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For removal of mature and immature Dictyocaulus vivapurus | 8 mg/kg PO | PO | Once | — | 🌎 NA |
| For treatment of susceptible nematodes | 7.5 mg/kg PO | PO | Once | — | 🌎 NA |
Goats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| For removal of mature and immature Dictyocaulus vivapurus | 8 mg/kg PO | PO | Once | — | 🌎 NA |
| For treatment of susceptible nematodes | 7.5 mg/kg PO | PO | Once | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Levamisole is an imidazothiazole derivative primarily utilized as an antinematodal parasiticide in large animals and, historically, as a microfilaricide and immunostimulant in small animals.
Clinical Pearls:
- Declining Use in Small Animals: Due to its narrow therapeutic index and the advent of safer, more efficacious anthelmintics (e.g., macrocyclic lactones, benzimidazoles), levamisole is rarely used in modern canine and feline practice.
- Large Animal Utility: It remains a valuable broad-spectrum anthelmintic in cattle, sheep, and swine, particularly effective against gastrointestinal and lung nematodes, though parasite resistance is an increasing global concern.
- Immunomodulation: Its unique ability to stimulate cell-mediated immunity has led to off-label use as an adjunctive therapy for chronic infections, immune-mediated diseases, and certain neoplasms, particularly in immunocompromised patients.
Mechanism of action
Antiparasitic Action: Levamisole acts as a cholinergic agonist at nicotinic acetylcholine receptors on the nematode muscle.
- Receptor activation → continuous depolarization → spastic paralysis of the worm.
- The paralyzed nematodes are subsequently expelled alive from the host's gastrointestinal or respiratory tract.
- At higher concentrations, it interferes with nematode carbohydrate metabolism by blocking fumarate reduction and succinate oxidation.
Immunostimulant Action: The exact mechanism is not fully elucidated. It is believed to:
- Restore cell-mediated immune function in peripheral T-lymphocytes.
- Stimulate phagocytosis and chemotaxis by monocytes and macrophages.
- Effects are generally more pronounced in immunocompromised animals rather than healthy ones.
Safety & warnings
Contraindications
- Lactating dairy animals (not approved)
- Severely debilitated animals
- Patients with significant renal or hepatic impairment
- Cats with FIV or FIP (and likely ineffective in FeLV)
- Use as a dirofilarial adulticide
- Intravenous (IV) administration (never recommended)
- Intramuscular (IM) administration in birds (avoid if possible)
Adverse effects
- Cattle: Muzzle foaming, hypersalivation, excitement, trembling, lip-licking, head shaking, injection site swelling
- Sheep/Goats: Transient excitability, depression, hyperesthesia, salivation, stinging upon SC injection
- Swine: Salivation, muzzle foaming, coughing/vomiting (especially if infected with lungworms)
- Dogs: GI disturbances (vomiting, diarrhea), neurotoxicity (panting, shaking, agitation), immune-mediated anemia, agranulocytosis, dyspnea, pulmonary edema, immune-mediated skin eruptions (erythema multiforme, toxic epidermal necrolysis), lethargy
- Cats: Hypersalivation, excitement, mydriasis, vomiting
Precautions
Narrow Margin of Safety: Levamisole has a narrow therapeutic index, especially in small animals and birds. Accurate dosing is critical.
- Stress: Use cautiously or delay use in cattle that are stressed due to vaccination, dehorning, or castration.
- Pregnancy: FDA Category C / Papich Class C. Has been implicated in causing abortion in goats. Use only if potential benefits outweigh risks.
- Nursing: Excreted in cows' milk; use with caution in nursing dams.
Drug interactions
Aspirin
Levamisole may increase salicylate levels
Chloramphenicol
Fatalities have been reported after concomitant administration; avoid using these agents together
Cholinesterase-inhibiting drugs (e.g., organophosphates, neostigmine)
Could theoretically enhance the toxic effects of levamisole; use together with caution
Nicotine-like compounds (e.g., pyrantel, morantel, diethylcarbamazine)
Could theoretically enhance the toxic effects of levamisole; use together with caution
Warfarin
Increased risk for bleeding
Monitoring
- Clinical efficacy (fecal exams, resolution of clinical signs)
- Adverse effects/toxicity observation
Pharmacokinetics
Half-life
Dogs1.8-4 hours
Absorption
Absorbed from the gut after oral dosing and through the skin after dermal application, although bioavailabilities are variable.
Distribution
Reportedly distributed throughout the body.
Metabolism
Primarily metabolized in the liver.
Elimination
Metabolites are excreted primarily in the urine (with less than 6% excreted unchanged) and in feces.
Overdose
Signs of levamisole toxicity often mimic those of organophosphate toxicity due to its cholinergic effects.
- Clinical Signs: Hypersalivation, hyperesthesias, irritability, clonic seizures, CNS depression, dyspnea, defecation, urination, and collapse. Acute overdosage can result in death due to respiratory failure. Cardiac arrhythmias may also be seen.
- Avian Toxicity: In pet birds, 40 mg/kg SC is reported as a toxic dose. IM injections may cause more severe toxicity. Signs include depression, ataxia, leg/wing paralysis, mydriasis, regurgitation, and death.
- Treatment: Primarily supportive, as animals generally recover within hours of dosing. If respiratory failure occurs, institute artificial ventilation with oxygen until recovery. For recent oral ingestion, emptying the gut and/or administering activated charcoal with cathartics may be indicated.
- Warning: Intravenous (IV) administration is particularly hazardous and is never recommended.
Available products
Formulations
- Injection (13.65% levamisole phosphate)
- Water Medication/Soluble Powder (18.15g, 46.8g)
- Oral Tablets/Boluses (184 mg, 2.19 g)
Veterinary
- Levamisole Phosphate Injection: 136.5 mg/mL (13.65%)
- Levamisole Hydrochloride Water Medication: 18.15 grams
- Levamisole Hydrochloride Soluble Drench Powder: 46.8 grams/packet
- Levamisole HCl Oral Tablets/Boluses: 184 mg, 2.19 gram
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Levamisole hydrochloride products should be stored at room temperature (15-30°C); avoid temperatures greater than 40°C. Levamisole phosphate injection should be stored at or below 21°C (70°F); refrigeration is recommended and freezing should be avoided. Compounded oral solution (25 mg/mL) retains >97% potency for 90 days when stored at 4°C and 25°C and protected from light.
Client information
- Strict Dosing: Give this medication exactly as prescribed by your veterinarian. Levamisole has a narrow margin of safety, meaning the difference between an effective dose and a toxic dose is small.
- Adverse Effects: Watch your pet closely for signs of toxicity such as excessive drooling, shaking, panting, vomiting, diarrhea, or unusual behavior. Contact your veterinarian immediately if these occur.
- Administration: Do not give on an empty stomach or immediately after your pet drinks water if using orally for certain conditions (follow specific vet instructions).
- Food Animals: Levamisole is not FDA-approved for use in dairy animals of breeding age. Adhere strictly to slaughter withdrawal times (e.g., 48 hours for cattle, 72 hours for sheep/swine).
- Retreatment: Animals in heavily parasitized environments may need retreatment 2-4 weeks after the initial dose.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.