Clorsulon

Clorsulon is a sulfonamide-derived flukicide used mainly for Fasciola hepatica infection in cattle. It is supplied alone in some regimens and as a partner in ivermectin-containing products. Its contribution in these combinations is fluke control, while ivermectin provides activity against susceptible nematodes and arthropods.

Group

Sulfonamide flukicide

Mechanism of Action

Clorsulon inhibits fluke glycolytic enzymes, including phosphoglycerate kinase and phosphoglycerate mutase. Blocking this pathway restricts an important source of ATP and leads to energy depletion and death. Systemic distribution in plasma and erythrocytes exposes susceptible flukes during feeding. Stage-dependent response varies with the formulation and extent of drug exposure.

Dose Rates

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Fasciola hepatica infection	7 mg/kg	PO	Once	Oral regimen; not effective against early immature flukes less than about eight weeks old.
Adult fluke with ivermectin-susceptible parasites	2 mg/kg	SC	Once	Ivomec Plus combination delivers ivermectin 0.2 mg/kg at this clorsulon dose; cattle only.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Fasciola hepatica infection	7 mg/kg	PO	Once	Oral regimen; not effective against early immature flukes less than about eight weeks old.

Llamas

Use / stage	Dose	Route	Schedule	Instructions
Fasciola hepatica infection	7 mg/kg	PO	Once	Oral regimen; not effective against early immature flukes less than about eight weeks old.

Indications

Treatment of susceptible adult Fasciola hepatica infection in cattle, including with an appropriate ivermectin–clorsulon combination.
Treatment of supported late-immature F. hepatica infection using a regimen with evidence for that developmental stage.
Selected treatment of susceptible Fasciola infection in other ruminants, with species- and regimen-specific evidence.

Contraindications

Cited products exclude female dairy cattle of breeding age.
Ivermectin/clorsulon cattle injections are not for dogs and are SC only.

Interactions

No specific clorsulon interaction established in the supplied monograph; combination ivermectin adds its own risks.

Adverse effects

Oral adverse effects are uncommon; injection-site swelling may occur with combination products.

Toxicity

A broad oral safety margin is described; manage clinically significant overdose supportively and assess the other active in combinations.

Preparations

Preparation	Form	Strength	Route
Curatrem oral drench 8.5%	Oral Liquid	85 mg / mL	PO
Ivomec Plus injection 100/10 mg per mL Clorsulon-based calculation only for the matching 2 mg/kg combination regimen; not a substitute for 7 mg/kg oral clorsulon. Do not use the 7 mg/kg oral clorsulon dose with this injectable combination.	Injection	clorsulon 100 mg / mL + ivermectin 10 mg / mL	SC

Monitoring and Administration

Oral 7 mg/kg has activity against flukes from about eight weeks; the 2 mg/kg injectable combination principally targets adults. It does not treat rumen flukes.

Shake oral suspension and assess efficacy. Product withdrawal: Curatrem cattle meat 8 days; Ivomec Plus meat 49 days, with dairy restrictions.