Phoxim is an antiparasitic active ingredient used in veterinary medicine in livestock against external parasites (mites, ticks, etc.). It is also used against agricultural pests. It belongs to the chemical class of the organophosphates.
EFFICACY AGAINST PARASITES
Efficacy against a specific parasite depends on the delivery form and on the dose administered. 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.
Click here for general information on features and characteristics of PARASITICIDES.
Oral LD50, rat, acute*: 1400 to 10000 mg/kg (depending on the studies)
Dermal LD50, rat, acute*: 1100 to 1200 mg/kg
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.
MRL (maximum residue limit) set for animal tissues (e.g. beef, mutton pork or chicken)*:
- CODEX: Yes
- EU: Yes
- USA: No
- AUS: No
* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock. MRL's for animal tissues may be set also for agricultural pesticides that are not approved for use on animals but are used on commodities fed to animals. A MRL may be also set in the form of an IMPORT TOLERANCE for active ingredients not approved in a particular country but approved for imported animal commodities.
Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.
Learn more about phoxim safety (poisoning, intoxication, overdose, antidote, symptoms, etc.).
General safety information for antiparasitics is available in specific articles in this site (click to visit):
- General safety of antiparasitics for domestic animals
- General safety of antiparasitics for humans
- General safety of antiparasitics for the environment
Never use products for livestock on dogs and cats, unless they are explicitly approved for both livestock and pets. Pets may not tolerate livestock formulations.
Never use agricultural or hygiene products with this or any other active ingredient on livestock or pets, even if there are veterinary products with this same active ingredient approved for use on animals. The formulations for agricultural or hygiene use are different and may be toxic for livestock or pets.
It is obvious that veterinary products are not intended for and should never be used on humans!!!
MARKETING & USAGE
Decade of introduction: 1960
Introduced by: BAYER
Some original brands: SEBACIL, SARNACURAN, BAYTHION
Patent: Expired (particular formulations may be still patent-protected)
Use in LIVESTOCK: Yes, scarce and declining, as all organophosphates
Use in HORSES: No
Use in DOGS and CATS: No
Main delivery forms:
Use in human medicine: No
Use in public/domestic hygiene: Yes
Use in agriculture: Yes
Generics available: Yes, very few
On livestock: Yes, as for all organophosphates: very frequent worldwide in such species as cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), houseflies (Musca domestica), mosquitoes.
Phoxim is a classical, veteran parasiticide belonging to the organophosphates. It was moderately used in sheep, goats and pigs in the 1970's to 1990's, in concentrates for dipping and spraying and in ready-to-use pour-ons. But usage has strongly declined since the introduction of systemic acaricides and lousicides (e.g. macrocyclic lactones). It is not used on pets.
Efficacy of phoxim
Regarding its veterinary usage, phoxim is a rather "specialized" organophosphate, used exclusively on sheep, goats and pigs against lice and scab and mange mites. It is especially effective and suited against these sheep parasites, because it is easily solved in wool lipids from where it is slowly released, which allows rather long protection periods.
Phoxim was one of the very few organophosphates originally available as a pour-on for pigs: most organophosphates are not suited for such a formulation but have to be used for dipping or spraying, basically because they are too toxic as pour-ons. Instead, phoxim shows a rather low toxicity to mammals.
However, resistance of important veterinary parasites to all organophosphates is widespread, e.g. in sheep lice (Damalinia ovis). The same applies to all other organophosphates. This is also a reason for their progressive replacement with newer active ingredients with a different mode of action.
Pharmacokinetics of phoxim
Percutaneous absorption (i.e. through the skin) of topically administered phoxim depends on the animal species, the administered dose, and the extension of the treated body surface. Studies on piglets treated with a phoxim pour-on showed that a maximum of 3% of the administered dose was absorbed into the bloodstream. Absorbed phoxim is quickly and vastly metabolized and excreted, mainly through urine (aprox. 80%) and feces (up to 12%). Highest residues were detected in fat tissues, liver and kidneys.
Mechanism of action of phoxim
As all organophosphates insecticides, phoxim acts on the nervous system of the parasites (but also of mammals, birds, fish and many organisms!) as inhibitor of acetylcholinesterase (also known as AchE), an enzyme that hydrolyzes acetylcholine (Ach). Ach is a molecule involved in the transmission of nervous signals from nerves to muscles (so-called neuromuscular junctions) and between neurons in the brain (so-called cholinergic brain synapses).
AchE's role is to terminate the transmission of nervous signals where Ach is the neurotransmitter (there are several other neurotrasmitters). By inhibiting the activity of AchE, carbamates prevent the termination of those nervous signals, i.e. the neurons remain in constant activity and excitation, massively disturbing the normal movements of the parasites. The bottom line for the parasites is that they are paralyzed and die more or less quickly. Organophosphates bind irreversibly to AchE, in contrast with carbamates, another chemical class of parasiticides, which bind reversibly to AchE.
Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.