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Pyrethrin

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Pyrethrin, RID, A-200, Piperonyl Butoxide, Pyrethrum Extract

  • See Also
  1. Permethrin
  2. Pyrethroid Toxicity
  3. Pesticide
  • Indications
  1. Pediculosis (Lice)
  • Contraindications
  1. Ragweed allergy (relative; may cross-react to Pyrethrins)
  • Mechanism
  1. Pyrethrins are Insecticides extracted from chrysanthemums
    1. Pyrethroids are longer acting derivatives (Permethrin)
  2. RID is a combination of Pyrethrin and Piperonyl Butoxide
    1. Piperonyl Butoxide is a synthetic derivative of benzodioxole
    2. Piperonyl Butoxide is an Insecticide synergist that inhibits Insect microsomal enzyme detoxification activity
    3. Piperonyl Butoxide is toxic if ingested (Seizures, hepatotoxicity, nephrotoxicity, carcinogenic)
  3. Pesticide Agents related to Pyrethrins
    1. Allethrin
    2. Cyfluthrin
    3. Cypermethrin
    4. Deltamethrin
    5. Dimethrin
    6. Fenothrin
    7. Fenvalerate
    8. Permethrin
    9. Remethrin
  • Background
  1. Advantages
    1. Available without a prescription
    2. Convenient (only 10 minute application)
  2. Disadvantages
    1. Does not kill all unhatched eggs
    2. Requires repeat application in 5-7 days
    3. Treatment failures are common
  • Medications
  1. Pyrethrin with Piperonyl Butoxide (RID)
    1. Shampoo: 60, 120, 240 ml
  • Dosing
  • Lice Treatment
  1. Apply Shampoo to involved area and avoiding mucous membranes
  2. Wash after 10 minutes
  3. Reapply Shampoo in 5-7 days
  • Adverse Effects
  1. See Pyrethroid Toxicity
  2. Mechanism
    1. Nerve toxicity is rare in humans
    2. Minimal absorption and rapid hepatic metabolism
  3. Effects
    1. Allergic Reaction in 1-3%
      1. Nasal congestion
      2. Asthma exascerbation
    2. Topical effects
      1. Paresthesias (hands and face)
    3. Rare neurologic effects
      1. Seizures
      2. Tremor
      3. Incoordination
  • Safety
  1. Pregnancy Category C
  2. Unknown safety in Lactation
  • Resources
  1. Piperonyl Butoxide and Pyrethrum Extract Shampoo (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=03769180-6c9e-4d6c-ad0f-43aea9b9ad71