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Aina Meducci 2012


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Pyrethrins and pyrethroids toxicity

Just about going to sleep when suddenly my brother says our persian-mixed cat licking the excess chrysanthemum tea from his cup. I told him no! because I remembered what our prof told us in class regarding chrysanthemum toxicity. See, being a vet makes you know everything about do and dont's in animal!


Nice tea..but,,

What are Pyrethrins?

Extracted from dried flowers of the chrysanthemum cinerariaefolium, natural pyrethrins are insect repellents. Both natural pyrethrins and synthetic ones called permethrins are used in insecticides and pet flea and tick products.

Chrysanthemum cinerariaefolium

What are pyrethroids?

Pyrethroids (allethrin, alphacypermethrin, bioremethrin, cypermethrin, deltamethrin, fenvalerate. permethrin, phenothrin, resmethrin, tetramethrin) are synthetic pyrethrins.

Pyrethrins and pyrethroids are used in as insecticides for the treatment of endoparasitic infestation. They are use in cats, dogs, sheep, cattle, poultry, horses, goats and humans. They are used in dogs for the control of fleas and lice. Preparations are available as dusting flowers, shampooa and sprays.

Flea spray containing pyrethrin

Shampoo containing pyrethrin

Toxic Dose

Varies depending upon type of pyrethroid, size of animal, and species.

Mechanism of toxicity

Toxicity may arise from self-grooming of treated hair. Occasionally, toxicity may arise from animals being in close association with or grooming treated animals

The toxic effects of pyrethroids and pyrethrins are due to alteration of the kinetics of voltage dependent sodium channels in nerves membrane, which causes repetitive discharge or membrane depolarisation (sodium unable to get out). Some pyrethroids may also inhibit GABA receptors causing loss inhibition. This can lead to hyperexcitability of nervous tissues and maybe the mechanism by which these compound produce convulsion.

Convulsion (seizures)

Natural pyrethrins are broken down by digestive juices, while the liver metabolizes synthetic pyrethrins before they enter an animal's GI tract. Pyrethrin toxicity in cats occurs because their livers are incapable of properly metabolizing synthetic pyrethrins.

All pyrethrins are easily hydrolyzed and degraded by stomach acids so toxicity following ingestion by pets is very low. Toxicities, although rare, do occur. A cat or dog with pyrethrin toxicosis generally will salivate, tremor, vomit, and may seizure. Generally, signs of toxicosis will be gone after 24 hours. Pyrethrins are some of the safest ingredients available, especially when one expects ingestion may occur, as is the case of cats and kittens. If lactating, breeding or pregnant animals must be treated for external parasites, pyrethrins are often recommended. Pyrethrins are generally safe for kittens as young as 4-6 weeks of age.

Clinical effect

Onset is usually 1-3 hours, sometimes up to 12 hours. Effects may have duration of 1-3 days. Simultaneous exposure to organophosphate insecticides may increase the toxicity of pyrethroids and pyrethrins. Piperonyl butoxide often added as a synergist to delay metabolism and increase toxicity in insects, produces effects similar to that of pyrethrins and pyrethroids. The clinical signs are shown below

  • Vomiting
  • Diarrhea
  • Ataxia
  • Tremor
  • Twitching
  • Dilated pupils
  • tachycardia
  • Pyrexia
  • Hyperexatability
  • Thirst
  • Fasciculation
  • Convulsions
  • Hyperaesthesia


If within 2 hours of ingestion, induce vomiting or perform gastric lavage and then administer adsorbents


  • Xylaxine (0.2mg/kg IV, 0.5-1 mg/kg SC or IM)
  • Apomorphine (0.005 mg/kg IV/IM, 0.1 mg/kg SC)

  • Activated charcoal (2 g/kg IM/SC)

Treatment thereafter is essentially symptomatic and supportive. Cats exposed to topical forms of synthetic pyrethrins should be thoroughly bathed with mild dish soap and lukewarm water. Overly warm water may enhance absorption of the pyrethrins, worsening the symptoms. For cats with minimal exposure this treatment may be enough.If the cat has absorbed lots of synthetic pyrethrins, she may need treatment with an anti-seizure medication like diazepam and/or the anti-tremor medication methocarbynol along with IV fluids to balance her electrolytes.

The body temperature is monitored, especially after bathing, as hypothermia increases the toxicity. Other treatments include anticonvulsants and/or muscle relaxants for controlling the seizures, and providing a safe environment to prevent injury resulting from the incoordination and disorientation. Atropine can be used to help decrease some of the signs such as the drooling. Fluids are generally administered.

Most pets recover from pyrethrin intoxication within 24-48 hours; recovery from pyrethroids may take longer. If no improvement is seen within 24 hours with treatment, the pet should be reevaluated.

" Pyrethrin is NOT the same as permethrin. Permethrin is a synthetic pyrethrin, and is less easily broken down than pyrethrin. Although its toxicity is relatively low, it is higher than that of pyrethrin. Pyrethrins can be used on cats; permethrins should NOT be used on cats. "

Sources: Handbook poisoning of dogs and cats, Blackwell science, pyrethrins and pyrethroid www.petseducation.com, The use of pyrethrins and pyrethroids in cats and dogs www.peteducation.com, Pyrethrins toxicity in cats.

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adnan Khan said...

if someone is poisoned slowly by mentioned above there is no remedy i m suffering from such in very subtle way(adnan shahzad pakistan pentasakhan@gmail.com

adnan Khan said...

Permethrin manufacture should be stopped as it is a subtle poison that kills sex and may deteriorate reproductive organs and cause psychosis, and a series of symptoms that is hazardous in nature manifested by it including genetic changes besides the symptoms articulated above.

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