Diazinon is an antiparasitic active ingredient used in veterinary medicine in dogs and livestock against external parasites (lice, mites, fleas, flies, ticks, etc.). It is also used against agricultural and household pests. It belongs to the chemical class of the organophosphates.
Common name: DIAZINON = DIMPYLATE
EFFICACY AGAINST PARASITES
Type of action: Broad spectrum contact, non systemic ectoparasiticide: insecticide, acaricide, tickicide, louisicide, larvicide
Main veterinary parasites controlled: flies, lice, fleas, mosquitoes, ticks, mites, blowfly strike, etc.
Efficacy against a specific parasite depends on the delivery form and on the dose administered.
Click here for general information on features and characteristics of PARASITICIDES.
Click here to view the article in this site with the most common dosing recommendations for diazinon used in domestic animals.
Oral LD50, rat, acute*: 1250 mg/kg
Dermal LD50, rat, acute*: >2150 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: Yes
- AUS: Yes
* 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 diazinon 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: 1950
Introduced by: GEIGY (→ CIBA-GEIGY → NOVARTIS)
Some original brands: NEOCIDOL, TOPCLIP, BASUDIN
Patent: Expired (particular formulations may be still patent-protected)
Use in LIVESTOCK: Yes, abundant, but declining, as all organophosphates
Use in HORSES: Yes, scarce and declining, as all organophosphates
Use in DOGS and CATS: Yes, moderate, but declining, as all organophosphates
Main delivery forms:
Use in human medicine: No
Use in public/domestic hygiene: Yes
Use in agriculture: Yes
Generics available: Yes, a lot
- In livestock & horses: 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), blowfly strike (Lucilia spp) and mosquitoes.
- In pets: Yes, quite frequent worldwide in dog and cat fleas (Ctenocephalides spp)
Diazinon is a classical, veteran parasiticide belonging to the organophosphates. Diazinon is exactly the same as dimpylate. In some countries, dimpylate is the official common name for veterinary use, whereas diazinon is the official common name for agricultural and hygiene uses.
There are also mixtures, mainly with synthetic pyrethroids.
Diazinon has been used a lot in the 1960's to 1990s, both in livestock and pets, as well as in agriculture, public and domestic hygiene.
In dogs and cats it is still used in numerous collars as well as shampoos, soaps, baths, sprays and the like, but its use has strongly declined after the introduction of more modern and safer flea and tick control spot-ons (= pipettes) and tablets.
However, there is a clear trend to replace all organophosphates with less toxic compounds, and diazinon products have been withdrawn or strongly restricted in several countries in the last years (e.g. sheep products in Australia and UK, pet collars in France, etc.).
Efficacy of diazinon
As most organophosphates diazinon is a broad-spectrum insecticide, acaricide and larvicide. It is especially effective against scab and mange mites (Psoroptes spp, Sarcoptesspp., etc.), flies, fleas, lice, blowfly strike, and insects in general, but less effective against ticks.
However, resistance of important veterinary parasites to all organophosphates, including diazinon is widespread, especially in cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), mosquitoes, dog and cat fleas (Ctenocephalides spp) and houseflies (Musca domestica). As a consequence, products with this active ingredient may not achieve the expected efficacy in many places. The same applies to all other organophosphates. This is also a reason for their progressive replacement with newer active active ingredients with a different mode of action.
Pharmacokinetics of diazinon
Percutaneous absorption (i.e. through the skin) of topically administered diazinon depends on the animal species, the administered dose, and the extension of the treated body surface. As a general rule, only a relatively low amount is absorbed into blood after topical administration. Animals treated topically can ingest diazinon through licking and grooming.
Ingested diazinon is vastly absorbed into blood and quickly metabolized. Half-life of ingested diazinon is about 12 hours. In dogs 58% is excreted through urine in the first 24 hours after administration, >85% in the form of various metabolites.
One of the main metabolites, diazoxon is an acetylcholinesterase inhibitor substantially more potent than diazinon itself.
Mechanism of action of diazinon
As all organophosphate insecticides, diazinon 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.