Brand: PARAMITE ® LA Insecticidal Spray & Backrubber

Company: VET-KEM

FORMULATION: liquid concentrate for spraying animals

ACTIVE INGREDIENT(S): Phosmet: 11.75% = 117.5 g/L

CHEMICAL CLASS of the active ingredient(s): Organophosphate

INDICATIONS: CATTLE (Beef & no-lactating dairy cows) & SWINE

PARASITES CONTROLLED (spectrum of activity)


Beef & non-lactating Dairy Cattle

  • Against cattle ticks, southern cattle ticks (Rhipicephalus = Boophilus microplus):
    • Spray: Dilute 1 gal Paramite L.A. in 240 gal of water OR 1 quart Paramite L.A. in 60 gal of water OR 1 cup Paramite L.A. in 15 gal of water. Phosmet concentration in final dilution: ~490 ppm* = mg/L = 0.049% active ingredient.
  • Against horn flies:
    • Spray: Dilute 1 gal Paramite L.A. in 200 gal of water OR 1 quart Paramite L.A. in 50 gal of water OR 1 cup Paramite L.A. in 12.5 gal of water. Phosmet concentration in final dilution: ~588 ppm* = mg/L = 0.0588% active ingredient.
    • Backrubber: Use fuel oil or other suitable carrier. Charge backrubber device or soak sack or cloth, as required. Retreat backrubber, as needed. Dilute 1 gal Paramite L.A. in 50 gal of oil OR 1 quart Paramite L.A. in 12.5 gal of oil OR 1 cup Paramite L.A. in 3.10 gal of oil. Phosmet concentration in final dilution: ~2350 ppm* = mg/L = 0.235% active ingredient.
  • Against lice:
    • Spray: Dilute 1 gal Paramite L.A. in 150 gal of water OR 1 quart Paramite L.A. in 38 gal of water OR 1 cup Paramite L.A. in 9.5 gal of water. Phosmet concentration in final dilution: ~783 ppm* = mg/L = 0.0783% active ingredient.
  • Against: Sarcoptic mange, winter ticks (Dermacentor albipictus), Lone Star ticks (Amblyomma americanum), Gulf Coast ear ticks (Amblyomma maculatum)
    • Spray: Dilute 1 gal Paramite L.A. in 100 gal of water OR 1 quart Paramite L.A. in 25 gal of water OR 1 cup Paramite L.A. in 6.2 gal of water. Phosmet concentration in final dilution: ~1175 ppm* = mg/L = 0.1175% active ingredient.


  • Against Lice, sarcoptic mange:
    • Spray: Dilute 1 gal Paramite L.A. in 100 gal of water OR 1 quart Paramite L.A. in 25 gal of water OR 1 cup Paramite L.A. in 6.25 gal of water. Phosmet concentration in final dilution: ~1175 ppm* = mg/L = 0.1175% active ingredient.

* ppm = parts per million


  • LD50 (acute oral) in rats: for the a.i. 113 mg/kg
  • LD50 (acute dermal) in rats: for the a.i. >4640 mg/kg
  • Estimated hazard class according to the WHO: II, moderately hazardous

Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)

  • Meat:
    • Cattle: USA: 3 days
    • Swine: USA 1 day
  • Milk for human consumption: USA Not approved for use on lactating dairy cows.

WARNING !!!: Never use on humans, dogs or cats.

Phosmet and all organophosphates (e.g. coumaphos, diazinon, dichlorvos, etc.) etc. are highly toxic to birds, fish and aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not contaminate water when cleaning equipment or disposing of equipment washwaters.

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? YES; cases of resistance of horn flies to organophosphates have been reported in the USA and elsewhere, but resistance to organophosphates is usually weaker and less widespread than to synthetic pyrethroids (e.g. permethrin). Resistance of most tick species, lice and mites (both of cattle & swine) to organophosphates is usually not a problem in most of the USA.

This means that if this product does not achieve the expected efficacy against horn flies, it may be due to resistance. However incorrect use is usually the most frequent cause of product failure.

Alternative chemical classes/active ingredients to prevent resistance of external parasites through product rotation:

These alternative products may not be available in all countries, or may not be available for spraying, or may not be effective against all the concerned parasites.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?


*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: USA
GENERIC BRANDS available? YES, but rather few, if at all. This brand with generic phosmet is marketed by VET-CHEM in the USA.

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used antiparasitic spray, dip & dust BRANDS click here.


This product is one of the few products containing organophosphates (=OP) left for spraying animals against external parasites (flies, liceticks, etc.). Liquid concentrates containing organophosphates were widely used between their discovery (~1950) and the 1990s. But subsequently most of them have been withdrawn and replaced by concentrates with less toxic synthetic pyrethroids (e.g. permethrin) or by more convenient ready-to-use pour-ons (mainly with macrocyclic lactones such as ivermectin, or synthetic pyrethroids). Against horn flies organophosphates (mainly diazinon) are still widely used in insecticide-impregnated ear-tags.

Insecticide concentrates for spraying and dipping such as this product often represent the cheapest option for insect control on animals. However the active ingredients used in such products are mostly rather old (introduced in the 1950s to 1970s) and many pests have developed resistance to them. More modern and more effective active ingredients for the control of external parasites are often not available as concentrates but only as ready-to-use pour-ons, injectables, or in the form of insecticide-impregnated ear-tags. They are usually more effective, more convenient and with a longer protection period than the concentrates, but are also more expensive and often not approved for the control of as many pests as the concentrates.

All organophosphates are veteran pesticides developed in the 1950s-1960s and are basically contact insecticides. This means that when the parasite comes in contact with it (e.g. during the blood meal, after landing on a treated host, etc), the active ingredient that impregnates the host's hair coat penetrates through the cuticle (i.e. the "skin" of insects and other arthropods) into its organism and disturbs essential biological processes in the parasite's body, in this case its nervous system.

After administration to livestock or other animals, organophosphates do not have a systemic mode of action, i.e. they are not transmitted to the parasite through the blood or the host. Topically administered organophosphates are very poorly absorbed through the skin of the hosts, and what is absorbed is quickly broken down and/or excreted. Consequently the concentration reached in the blood is too low to kill blood-sucking parasites.

For best results it is very important to ensure a complete coverage of the animals' hair coat. Depending on size and hair coat, adult cattle need 3 to up to 10 liters dilution per head for complete wetting, swine need about 1 liter. For licemite and tick control it is also essential to ensure adequate coverage of the places where the parasites may hide (e.g. inside the ears, below the tail, the udders, etc.), otherwise a significant number of parasites will survive, reproduce and perpetuate the infestations. To learn more about spraying cattle and other livestock click here.

Backrubbers have and inherent weakness: Dosing depends on the behavior of the animals. It is unavoidable that some animals get too much product, and other animals not enough. Besides insufficient protection of some animals, this may cause excessive residues in other animals. For these reasons backrubber application is no more allowed in many countries (e.g. the EU, Australia, etc.). And it is generally accepted that underdosing of animals favors resistance development. To learn more about backrubbers for cattle click here.

Control of susceptible (i.e. non-resistant) horn flies is usually good, because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. Lice and mites are also exposed to insecticides for a long period of time because they never leave the host. Control of other flies (face flies, stable flies, horse fliesblack flies) and mosquitoes is insufficient because they may bite the treated animal anywhere in its body and remain attached and thus exposed to the insecticide only during their blood meals that last a few seconds or minutes, which is too short to kill them. Ticks attaching to the hosts in those body parts that are poorly covered with insecticide are also likely to survive.

Lice and mites spend their whole life on the infected animals but are likely to survive hidden inside the ears if they are not properly treated. And their eggs remain unaffected by the insecticide: this is why it is very important to re-treat the animals after 2-3 weeks, when most of the eggs laid before the previous treatment have already hatched.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.