Vetdrugs 2.0Closantel is a salicylanilide anthelmintic used mainly against liver flukes and selected blood-feeding parasites in ruminants. Persistent protein-bound exposure contributes to activity against parasites feeding on host fluids or tissues. The susceptible fluke stages and additional parasite spectrum depend on the host species and formulation.
Group
Salicylanilide anthelmintic
Mechanism of Action
Closantel acts as a proton ionophore and uncouples mitochondrial oxidative phosphorylation. Dissipation of the proton gradient separates electron transport from ATP production, depriving susceptible parasites of usable metabolic energy. This disrupts essential functions and leads to parasite death. Strong plasma-protein binding supports prolonged exposure of susceptible blood- or tissue-feeding stages.
Dose Rates
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible liver fluke and blood-feeding parasites | 10 mg/kg | PO | Once | Oral regimen; efficacy varies with parasite species, stage and resistance. |
Sheep
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Susceptible liver fluke and blood-feeding parasites | 10 mg/kg | PO | Once | Oral regimen; efficacy varies with parasite species, stage and resistance. |
Indications
- Treatment of susceptible late-immature and adult Fasciola infections in cattle and sheep with a corresponding product.
- Treatment of Haemonchus contortus or other specifically supported blood-feeding nematodes in ruminants.
- Treatment of sheep nasal-bot infestation caused by Oestrus ovis with an indicated formulation.
Contraindications
- Do not overdose; avoid use in species not supported by the formulation.
Interactions
- Other flukicides may duplicate treatment; combination doses require their own verified directions.
Adverse effects
- Anorexia, ataxia and visual disturbance, especially with overdose.
Toxicity
Overdose can cause retinal/optic nerve injury and permanent blindness. There is no specific antidote; prevent further exposure and provide supportive care.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Zenvet oral solution 15% 15% w/v = 150 mg/mL; do not inject. | Oral Liquid | 150 mg / mL | PO |
| Zenvet 1000 mg bolus | Tablet | 1000 mg / tablet | PO |
| Zenvet 6000 mg bolus | Tablet | 6000 mg / tablet | PO |
Monitoring and Administration
Weigh accurately and calibrate dosing equipment. Assess efficacy rather than repeating ineffective treatment in resistant fluke populations.
Oral and injectable products have different concentrations and directions; milk restrictions are product-specific.