Elephant Formulary

© 2003-17 Susan K. Mikota DVM and Donald C. Plumb, Pharm.D. Published by
Elephant Care International

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Elephant specific information, if available, is in blue.

Chemistry – A benzenesulfonamide, clorsulon has a chemical name of 4-amino-6-trichloroethenyl-1,3-benzenedisulfonamide.


Storage/Stability/Compatibility – Unless otherwise instructed by the manufacturer, clorsulon should be stored at room temperature (15-30°C).


Pharmacology – In susceptible flukes, clorsulon inhibits the glycolytic enzymes 3-phosphoglycerate kinase and phosphoglyceromutase, thereby blocking the Emden-Myerhof glycolytic path­way. The fluke is deprived of its main metabolic energy source and dies.


Uses/Indications – Clorsulon is approved for use in the treatment of immature and adult forms of Fasciola hepatica(Liver fluke) in cattle. It is not effective against immature flukes less than 8 weeks old. It also has activity against Fasciola gigantica. Although not approved, the drug has been used in practice in various other species (e.g., sheep, llamas). It has activity against F. magna in sheep, but is not completely effective in eradicating the organism after a single dose, thereby severely limiting its clinical usefulness against this parasite. Clorsulon is also not effective against the rumen fluke (Paramphistomum).


Pharmacokinetics – After oral administration to cattle, the drug is absorbed rapidly with peak levels occurring in about 4 hours. Approximately 75% of the circulating drug is found in the plasma and 25% in erythrocytes. At 8-12 hours after administration, clorsulon levels peak in the fluke.


Contraindications/Precautions/Reproductive Safety – No milk withdrawal time has been determined, and the drug is labeled not to be used in female dairy cattle of breeding age.


Clorsulon is considered to be safe to use in pregnant or breeding animals.


Adverse Effects/Warnings – When used as directed adverse effects are unlikely to occur with this agent.


Overdosage/Acute Toxicity – Clorsulon is very safe when administered orally to cattle or sheep. Doses of up to 400 mg/kg have not produced toxicity in sheep. A dose that is toxic in cattle has also not been determined.


Drug Interactions & Drug/Laboratory Interactions – None identified.


Doses –


For Fasciola hepatica infections:

a)   7 mg/kg PO; deposit suspension over the back of the tongue. (Label directions; Curatrem®—MSD-AgVet)



For Fasciola hepatica infections:

a)   7 mg/kg PO. (Fowler 1989)



a) Darunee Tuntasuvan B.Sc., D.V.M., Ph.D. (personal communication) 2003. In an unpubublished study, Dr. Tantasuvan found a mixture of 1% ivermectin and 10% Clorsulon (Ivomec – F) administered subcutaneously at a dose of 0.1 mg/kg to be 100 % effective against helminths. Flotation and sedimentation techniques were performed and eggs / gram determined at 0, 1, and 2 days and at weekly intervals for 6 weeks. This dose was not effective against flukes. For further information contact tdarunee@hotmail.com

Monitoring Parameters –

1) Clinical efficacy



Client Information – Shake well before using.


Dosage Forms/Preparations/FDA Approval Status/Withholding Times –

Clorsulon 8.5% (85 mg/ml) Oral Drench in quarts or gallons; Curatrem®  (Rhone Merieux); (OTC)  Approved for use in beef and non-lactating dairy cattle. Slaughter withdrawal= 8 days.