ISSN 2398-2969      

Phenoxy herbicide poisoning

icanis

Synonym(s): Phenoxy acids, Phenoxy acetic acids, Phytohormones: 2,4-D (2,4-dichlorophenoxyacetic acid), 2,4-DB, 2,4-MCPA (2-methyl-4-chlorophenoxyacetic acid), 2,4-MCPP (methylchlorophenoxy propionic acid or mecoprop), dichlorprop (2,4-DP), fenoprop (2-[2,4,5-trichlorophenoxy] propionic acid


Introduction

  • Selective herbicides that mimic plant growth hormones. Available as soluble concentrates or emulsions. These are a family of chemicals that are structurally similar, that are carboxylic acids in an acid or salt form.
  • Signs: common signs include dermal or ocular irritation, nauseas, vomiting and diarrhea - signs are usually self-limiting and respond well to minimal symptomatic and supportive care; high dose exposures in dogs can lead to myotonia; prolonged exposures may lead to renal or hepatic damage. 
  • Diagnosis: history of exposure, clinical signs, response to treatment.
  • Treatment: detoxification if appropriate, intravenous fluids to maintain hydration and assist in renal excretion, anti-emetic medications for persistent vomiting, bland diet.
  • Prognosis: excellent - renal/hepatic damage and fatalities are rare.

Pathogenesis

Etiology

  • Ingestion of herbicide.
  • Ingestion of treated plants.
  • Exposure to treated areas before herbicide has dried can result in percutaneous absorption.

Pathophysiology

  • Ingestion causes local irritation to and possible ulceration of mucous membranes of the mouth, pharynx and gastrointestinal tract. 
  • Compounds are readily absorbed from the gastrointestinal tract, skin and lungs.
  • Not significantly stored in fat.
  • Renal excretion is rapid except in dogs. 
  • Limited biotransformation to less toxic substances; majority of compounds are excreted unchanged in the urine.
  • Relatively low toxicity: acute oral LD50 in dogs is 100 mg/kg.
  • Uncouples oxidative phosphorylation, depresses ribonuclease synthesis, and increases paranitrophenyl phosphatase.

Timecourse

  • Most patients respond positively within 24-72 hours following acute exposures.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Referred papers

Other sources of information

  • Walton R A (2016) Blackwell's Five-Minute Veterinary Consult, Clinical Companion, Small Animal Toxicology. 2nd edn. Wiley Blackwell, Chapter 76: Herbicides. pp 565-570.
  • Chandler E A, Gaskell C J & Gaskell R M (1994) Feline Medicine and Therapeutics. 2nd edn. Oxford: Blackwell Scientific Publications. pp 660.

Organisation(s)

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