Chlorpyrifos is an antiparasitic active ingredient used in veterinary medicine in dogs and livestock against external parasites. It is also used against agricultural and household pests. It belongs to the chemical class of the organophosphates.
As most organophosphates, chlorpyrifos products are used for topical administration, either as concentrates (for dipping or spraying) or in ready-to-use larvicidal dressings, pour-ons and a few ear-tags for livestock. Usage in dogs is irrelevant. Chlorpyrifos is sometimes used in combination with other compounds (mainly synthetic pyrethroids). Nowadays usage has strongly declined in most regions because it has been replaced by newer, more effective and less toxic compounds.
Chlorpyrifos was banned in the USA in 2018.
Resistance to all organophosphates is already very frequent worldwide, particularly in cattle ticks, houseflies, mosquitoes, fleas, etc.
The table below indicates some usual dosing recommendations for chlorpyrifos issued by manufacturers or documented in the scientific literature. They may not be approved in some countries.
| Dosing recommendations for CHLORPYRIFOS |
||
| DOGS | ||
| Delivery | Parasites | Dose (against chlorpyrifos-susceptible parasites) |
| Dip, spray | Ticks, mites, lice | 420-700 ppm (=mg/L) in the wash, dep. on indication |
| CATTLE | ||
| Dip, spray | Ticks, flies, mites, lice | 240-500 ppm (=mg/L) in the wash, dep. on indications; for replenishment follow the label instructions |
| Pour-on | Ticks, flies, mites, lice | 3,5-14 mg/kg, dep. on weight and indications |
| SHEEP & GOATS |
||
| Dip, spray | Mites, lice | 375-450 ppm (=mg/L) in the wash, dep. on indications; for replenishment follow the label instructions |
| Pour-on | Mites, lice | 5-10 mg/kg, dep. on weight and indications |
| SWINE | ||
| Dip, spray | Mites, lice | 240-450 ppm (=mg/L) in the wash, dep. on indication |
| Pour-on | Mites, lice | 3,5-7 mg/kg, dep. on weight and indications |
| HORSES | ||
| Dip, spray | Ticks, flies, mites, lice | 240-450 ppm (=mg/L) in the wash, dep. on indications; for replenishment follow the label instructions |
| SOUTH AMERICAN CAMELIDS |
||
| Dip, spray | Ticks, mites, lice | 400 (=mg/L) in the wash, dep. on indications; for replenishment follow the label instructions |
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Dosing recommendations for antiparasitics depend on national regulations. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasite. Check the labels of the products available in your country for specific information on approved indications.
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