WHO Acute Hazard classification of pesticides: III, slightly hazardous

Mechanism of action of Lufenuron

Benzoylureas, as other Chitin Synthesis Inhibitors hamper the synthesis and/or the correct deposit of chitin in the cuticle of insects. As a consequence larvae or nymphs cannot properly molt and die during the molting process. Egg hatching is also interrupted due to the fact that young larvae developing inside the egg have to molt before hatching.

If the adult female was treated with a chitin synthesis inhibitor significant amounts of it are passed to the eggs. The embryo can develop normally but it dies during the first molt, still inside the eggshell.

Acute Toxicity and Tolerance of Lufenuron

  • LD50 acute, rats, p.o. >2000 mg/kg
  • LD50 acute, rats, dermal >4000 mg/kg.
  • Dogs and cats tolerate lufenuron very well.
  • The safety factor for dogs is >200
  • Dogs tolerated single oral doses of 200 mg/kg without adverse drug reactions. Oral treatment at 100 mg/kg during 3 consecutive days a month, during 3 months didn't cause toxic symptoms. Usual therapeutic dose: p.o. 10 to 30 mg/kg.
  • Cats tolerated single doses of up to 300 mg/kg as well as 150 mg/kg during three consecutive days a month, during 3 months without adverse drug reactions. Usual therapeutic dose: p.o. 30-60 mg/kg; s.c. 10-20 mg/kg.

Toxic Symptoms caused by Lufenuron Poisoning

  • As a general rule, intoxications with lufenuron are very infrequent due to its low toxicity, the high safety margin and the excellent tolerance in dogs and cats. 

Lufenuron Side Effects, Adverse Drug Reactions (ADRs) and Warnings

  • In cats, slight transient pain can happen after administration of the injectable suspension. A small lamp may appear at the injection site that subsides after several weeks.
  • After oral administration the following rare adverse drug reactions can happen: vomit, lethargy or depression, loss of appetite, diarrhea, difficult breathing, itching, reddened skin.
  • Never administer the injectable suspension to dogs: it can cause severe local reactions.
  • Do not use tablets for dogs in cats, and never use tablets for large dogs in small dogs. It happens that some users want to save money buying tablets for large dogs for treating smaller dogs (or even cats!) twice or more times. The risk of overdosing is considerable, either due to erroneous calculations or to unskilled manipulation. In addition, dog medicines may sometimes contain ingredients that are toxic to cats.

Antidote and Treatment of Lufenuron Intoxication

  • There is no antidote for lufenuron poisoning.
  • Treatment consists in preventing further exposure together with supportive and symptomatic measures.

Pharmacokinetics of Lufenuron

  • Lufenuron is quickly absorbed into blood, both after injection and oral administration. Subsequently it is deposited in the pet's body fat from where it is slowly released back to the bloodstream. This allows maintaining the effective concentration in blood for up to 6 months (after injection).
  • Lufenuron is hardly metabolized. It is slowly eliminated through the liver and the feces.

Environmental Toxicity of Lufenuron

  • Lufenuron is not or only slightly harmful to birds, fish amphibians (frogs, salamanders, etc.) and mollusks.
  • Lufenuron is toxic to aquatic invertebrates.
  • Lufenuron has potential for bioaccumulation in the environment and the food chain.
  • Lufenuron is not persistent in water or biologically active soils. Half-life in soil under aerobic conditions is 13-20 days.
  • Lufenuron binds strongly to soil particles.
  • Correctly used in dogs and cats lufenuron is unlikely to be detrimental for the environment.

Additional information

Click here for a list and overview of all safety summaries of antiparasitic active ingredients in this site.

  • Lufenuron is an insect growth regulator belonging to the chemical class of the benzoylureas.
  • Lufenuron is not used in livestock.
  • Lufenuron is not used in human medicines.
  • Lufenuron is used in crop pesticides.
  • Lufenuron is not used in public and domestic hygiene as a biocide.
  • Click here for General safety of antiparasitics for domestic animals.
  • Click here for General safety of antiparasitics for humans.
  • Click here for General safety of antiparasitics for the environment.
  • Click here for technical and commercial information on lufenuron.


If you intend to use a veterinary drug containing this active ingredient you must carefully read and follow the safety instructions in the product label.  Always ask your veterinary doctor, or pharmacist, or contact the manufacturer. Be aware that the safety instructions for the same veterinary medicine may vary from country to country.

The information in this page must not be confused with the Materials and Safety Datasheets (MSDS) officially issued by manufacturers for active ingredients and many other chemicals. MSDSs target safety during manufacturing, transport, storage and handling of such materials. This safety summary is a complement to the information on product labels and MSDS.

The toxicity of an active ingredient must not be confused with the toxicity of finished products, in this case parasiticidal drugs or pesticides. Finished products contain one or more active ingredients, but also other ingredients that can be relevant from the safety point of view.

All information in this site is made available in good faith and following a reasonable effort to ensure its correctness and actuality. Nevertheless, no this regarding guarantee is given, and any liability on its accuracy, integrity, sufficiency, actuality and opportunity is denied. Liability is also denied for any possible damage or harm to persons, animals or any other goods that could follow the transmission or use of the information, data or recommendations in this site by any site visitor or third parties.