Clorsulon: veterinary dose and monograph

At a glance

Drug class

Antiparasitic

Also known as

Curatrem, Ivomec Plus (component)

Species with doses

Cattle, Sheep and Camelids

General dose range

2–7 mg/kg PO single dose (repeat per cycle) — check the species tables for the indication

Routes

SC, PO

Last reviewed

1 October 2026

Indications

• Adult liver fluke (Fasciola hepatica) in cattle, sheep and goats
• Fluke control as part of combination endectocide therapy (with ivermectin)
• Immature fluke activity at the higher oral-drench dose

Clorsulon dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Cattle

• Adult liver fluke (combination injectable, 2 mg/kg): Plumb’s p.309 (Ivomec Plus label): 1 mL per 50 kg SC behind the shoulder (ivermectin 0.2 mg/kg + clorsulon 2 mg/kg); US slaughter withdrawal 49 days; not for lactating dairy cattle.
• Liver fluke (oral drench, incl. some immature): Plumb’s p.309 (Curatrem label): 7 mg/kg PO, deposited over the back of the tongue. US slaughter withdrawal 8 days; not for lactating dairy cattle.

Goats

• No reference dose for this species: Plumb’s gives cattle, sheep and llama doses but none for goats; Papich 5e has no clorsulon monograph.

Sheep

• Liver fluke: Plumb’s p.309 (Roberson 1988): sheep 7 mg/kg PO for Fasciola hepatica. Extra-label — obtain a withdrawal (FARAD).

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Adult liver fluke (combination injectable, 2 mg/kg): Plumb’s p.309 (Ivomec Plus label): 1 mL per 50 kg SC behind the shoulder (ivermectin 0.2 mg/kg + clorsulon 2 mg/kg); US slaughter withdrawal 49 days; not for lactating dairy cattle.
• Liver fluke (oral drench, incl. some immature): Plumb’s p.309 (Curatrem label): 7 mg/kg PO, deposited over the back of the tongue. US slaughter withdrawal 8 days; not for lactating dairy cattle.

Camelids

• Liver fluke (Fasciola hepatica): Plumb’s p.309 (Fowler 1989): llamas 7 mg/kg PO.

Contraindications

Lactating dairy animals producing milk for human consumption (residues — verify product). Known hypersensitivity. Use the correct dose for the target stage (the low injectable-combination dose targets adults only). Observe meat/milk withdrawal.

Species-specific warnings

Cattle: Not for lactating dairy producing human milk unless the specific product permits; observe meat/milk withdrawal.

Adverse effects

• Generally very well tolerated
• Rare transient GI/soft-stool
• Combination products: ivermectin-component effects (injection-site reaction, MDR1 caution if misused in dogs)

Drug interactions

• Combined with ivermectin in fixed products (complementary nematode + fluke spectrum)
• No significant systemic therapeutic drug interactions

Pregnancy and lactation

Considered safe in pregnant cattle/sheep at label doses; verify the specific product for dairy/breeding use.

Monitoring

• Faecal fluke egg counts / clinical response (chronic fasciolosis improves over weeks)
• Meat/milk withdrawal compliance
• Choice of dose/stage targeted (adult vs immature)

Toxicity and overdose

Wide safety margin; overdose is generally well tolerated. The main practical limitations are stage-specificity (poor against early immature flukes at the low combination dose) and residue/withdrawal compliance.

Management: Supportive; no specific antidote required. Manage any GI upset symptomatically.

Clinical pearls

• The fluke half of "Ivomec Plus"-type combos — it adds adult-Fasciola cover to ivermectin's nematode/ectoparasite spectrum
• Stage matters: the low combination dose targets ADULT flukes; the higher oral-drench dose reaches some immature stages
• For acute fasciolosis (early immature flukes), triclabendazole/nitroxynil are better — clorsulon shines for chronic adult-fluke burdens
• Observe the (longer) withdrawal of the combination injectable vs the oral drench

Mechanism of action

Clorsulon is absorbed and reaches the fluke via the host's blood (on which the fluke feeds); inside the parasite it inhibits the glycolytic enzymes 3-phosphoglycerate kinase and phosphoglyceromutase, blocking glucose metabolism and energy (ATP) production so the fluke starves and dies. Its action on adult, blood-feeding flukes explains why it targets mature stages best.

Formulations and products

• Oral drench 8.5 % (85 mg/mL, Curatrem)
• Injectable (with ivermectin, Ivomec Plus — 2 mg/kg clorsulon)
• Curatrem (Boehringer Ingelheim (Merial)) — Clorsulon 8.5 % oral drench, Oral drench
• Ivomec Plus (Boehringer Ingelheim) — Ivermectin + Clorsulon injectable, SC injection (combination)

Storage

Drench/injectable: 15–30 °C, protect from light/frost.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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Frequently asked questions