Pyrethroid

Aka: Pyrethroid, Pyrethroid Insecticide, Pyrethroid Toxicity, Pyrethroid Poisoning

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II. Mechanism: Insecticide

  1. Pyrethroids are synthetic antiparasitic agents based on Pyrethrins
  2. Derived from pyrethrum, a chemical found in Chrysanthemum cinerariifolum flowers
  3. Pyrethroids are highly liphophilic, allowing for the penetration and paralysis of Insects
    1. Neurotoxic at voltage sensitive Sodium channels, delaying their closure with secondary hyperexcitation

III. Mechanism: Toxicity

  1. Toxicity is uncommon outside of massive ingestions or Allergic Reaction
  2. Human absorption may occur with inhalation, ingestion or rarely via skin absorption
  3. Half-Life <8 hours
    1. Extended Half-Life when combined with Piperonyl Butoxide (a synergist added to Pyrethrins, Permethrin)

IV. Medications: Pyrethroid

  1. Type 1 Pyrethroids (lack cyano group; fast onset, lower Insect kill rate)
    1. Permethrin
    2. Allethrin
    3. Tetramethrin
    4. Resmethrin
    5. D-Phenothrin
    6. Bioresmethrin
  2. Type 2 Pyrethroids (contain cyano group; slow onset, higher Insect kill rate, less affected by Temperature)
    1. Cypermethrin
    2. Cyfluthrin
    3. Deltamethrin
    4. Cyphenothrin
    5. Fenvalerate
    6. Fluvalinate

V. Adverse Effects: Toxicity with Massive Ingestion or Allergic Symptoms

  1. Skin and Mucous Membrane
    1. Irritation
    2. Urticaria
  2. Gastrointestinal
    1. Vomiting
    2. Abdominal Cramping
    3. Diarrhea
  3. Cardiovascular
    1. Hypotension
    2. Tachydysrhythmia
  4. Lung
    1. Cough
    2. Bronchospasm
    3. Pulmonary Edema (type 2 Pyrethroids)
  5. Neurologic
    1. Headache
    2. Dizziness
    3. Hyperreflexia
    4. Type 1 Pyrethroids
      1. Tremor
      2. Paresthesias
    5. Type 2 Pyrethroids
      1. Coarse Tremor
      2. Choreoathetosis
      3. Seizures

VI. Management: Toxicity

  1. See Unknown Ingestion
  2. Skin Decontamination (soap and water)
  3. Hypotension
    1. Intravenous Fluids
    2. Norepinephrine for refractory Hypotension
  4. Seizures
    1. See Status Epilepticus
    2. Benzodiazepines
    3. Barbiturates
  5. Disposition
    1. Medical clearance for discharge at 4 to 6 hours after exposure if no neurologic or cardiopulmonary symptoms

VII. References

  1. Tomaszewski (2023) Crit Dec Emerg Med 37(6): 32

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