pyrethrins

Action and Spectrum

Actions and Spectrum: 

Neurotoxic Effects: pyrethrins primarily target the nervous systems of insects by disrupting their normal nerve function. They affect sodium ion channels in the nerve cell membranes, leading to increased permeability and prolonged opening of these channels. This results in repetitive nerve firing and paralysis in insects.  

Low Toxicity to Humans: pyrethrins are generally considered to have low toxicity to humans. This is because human sodium channels are less sensitive to pyrethrins compared to insect sodium channels. As a result, the neurotoxic effects observed in insects are much less pronounced in humans. 

Spectrum: 

Allergic Reactions: In some rare cases, individuals may develop allergic reactions to pyrethrins, resulting in more severe skin reactions, respiratory symptoms, or other allergic responses. However, these cases are infrequent. 

Drug Interaction

Adverse Reaction

Frequency not defined  

Dermatologic: stinging of the skin, pruritus, Burning sensation of skin, skin irritation, stinging of the skin  

Central nervous system: Localized burning 

Black Box Warning

Black Box Warning:  

Neurological Effects: pyrethrins exposure can lead to neurotoxic effects, such as tremors, convulsions, and paresthesia (tingling or numbness). In severe cases, it may result in seizures or other neurological complications.  

Respiratory Irritation: Inhalation of pyrethrins can cause respiratory irritation, leading to symptoms such as coughing, wheezing, shortness of breath, and nasal congestion.

Contraindication / Caution

Contraindication/Caution:  

Hypersensitivity or Allergy: Individuals who have a known hypersensitivity or allergy to pyrethrins or related compounds should avoid products containing these substances.  

Asthma or Respiratory Issues: Inhaling pyrethrins as fine mists or aerosols can potentially trigger or exacerbate respiratory symptoms in individuals with asthma or other pre-existing respiratory conditions. 

Sensitive Skin: People with sensitive or easily irritated skin may experience skin reactions when using pyrethrin-containing products, leading to redness, itching, rash, or dermatitis. 

Children and Infants: The utilization of products containing pyrethrin demands careful consideration when it comes to children and infants, as their still-developing physiques could potentially exhibit increased responsiveness to the compound’s impacts. It is imperative to exercise vigilance in preventing over-application or direct skin interaction. 

Pregnancy and Breastfeeding: Limited data is available regarding the safety of pyrethrins during pregnancy and breastfeeding. To ensure safety, it is recommended that pregnant and breastfeeding individuals seek advice from a medical practitioner before utilizing products that contain pyrethrins. 

Pregnancy / Lactation

Pregnancy warnings:     

Pregnancy category: N/A 

Lactation: Excreted into human milk is unknown 

Pregnancy Categories:         

Category A: Studies that were well-controlled and met expectations revealed no risk to the fetus in either the first or second trimester. 

Category B: There were a lack of studies on pregnant women and no evidence of risk to the fetus in animal experiments.   

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.   

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category

Pharmacology

Pharmacology:  

pyrethrins are natural insecticides derived from the flowers of certain chrysanthemum species. They have been used for many years in various pest control products, including insect sprays and shampoos for the treatment of head lice and scabies. 

Pharmacodynamics:  

pyrethrins exert their insecticidal effects by targeting the nervous system of insects. They interfere with the normal functioning of nerve cells, leading to hyperexcitation and paralysis. pyrethrins primarily affect sodium channels in the nerve cell membranes, leading to prolonged depolarization and disruption of nerve impulses. This ultimately results in paralysis and death of the insects. 

Pharmacokinetics: 

Absorption 

pyrethrins are primarily absorbed through inhalation, dermal contact, and ingestion. Inhalation exposure may occur during spray application, while dermal absorption can occur through direct skin contact. Ingestion could happen if contaminated hands or objects are brought to the mouth.  

Distribution 

Once absorbed, pyrethrins are rapidly distributed throughout the body via the bloodstream. They have a relatively short half-life, which limits their accumulation in tissues. The lipophilic nature of pyrethrins allows them to readily cross cell membranes, potentially leading to distribution in various tissues and organs. 

Metabolism 

pyrethrins are metabolized mainly in the liver through enzymatic processes. Metabolism generally involves hydrolysis and oxidation reactions. The metabolites produced are typically less toxic than the parent compounds. metabolism can vary between individuals and may be influenced by factors such as genetics and concurrent exposure to other chemicals. 

Excretion and Elimination 

metabolized pyrethrin metabolites are excreted primarily through the urine. The kidneys play a vital role in the filtration of these substances from the bloodstream into the urine, facilitating their removal from the body. Since pyrethrins have a short half-life, they are typically eliminated from the body relatively quickly, usually within a few days. 

Adminstartion

Administration:  

Typically, you would apply the pyrethrin product to dry hair and scalp. Be sure to cover all hair and scalp areas and massage the product in thoroughly. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: pyrethrins 

Why do we use pyrethrins?   

Lice and Parasite Treatment: pyrethrins have been used in shampoos and lotions for treating head lice and pubic lice infestations (pediculosis). These products are applied to the affected areas to kill the parasites. 

Scabies Treatment: pyrethrins can also be used to treat scabies, a skin condition caused by the Sarcoptes scabiei mite. Creams or lotions containing pyrethrins are applied to the skin to eliminate the mites.