pyrethrins/piperonyl butoxide

Action and Spectrum

Actions and Spectrum: 

Actions 

pyrethrins exert their insecticidal effects by targeting the nervous system of insects. They bind to sodium channels in the nerve cell membranes, leading to prolonged opening of these channels. This results in an increased influx of sodium ions, hyperexcitation of neurons, repetitive nerve impulses, and ultimately paralysis and death of the insect. pyrethrins have a fast onset of action and can cause immediate knockdown of insects upon contact or exposure. This rapid knockdown is due to their ability to quickly disrupt the normal functioning of the insect’s nervous system. 

Spectrum 

The combination of pyrethrins and PBO has a broad spectrum of activity against various insects, including mosquitoes, flies, fleas, ticks, lice, beetles, and other pests. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Edema 

Slight corneal erosion 

Burning 

Stinging 

Erythema 

Pruritus 

Urticaria 

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

• Allergic reactions 
• Asthma  
• Children/Pets 
• Aquatic life 
• Beneficial insects 
• Mixing with other chemicals 
• Pregnancy 
• Lactation 

Pregnancy / Lactation

Pregnancy consideration:  

Used as a drug of choice in pregnant females for the treatment. 

Breastfeeding warnings:  

Used as a drug of choice in lactating females for the treatment. 

Pregnancy category: 

Category A: well-controlled and satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

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: No data is available for the drug under this category. 

Pharmacology

Pharmacology:  

pyrethrins target the nervous system of insects by binding to sodium channels in neural membranes. This interaction leads to prolonged sodium channel opening, resulting in repetitive nerve impulses, paralysis, and, ultimately, the insect’s death. 

Pharmacodynamics: 

pyrethrins have a higher affinity for insect sodium channels than mammals. This selectivity contributes to their relative safety for mammals and their effectiveness as insecticides with minimal toxicity to humans and other mammals. 

PBO acts as a synergist when combined with pyrethrins. It enhances the insecticidal activity of pyrethrins by inhibiting specific enzymes, primarily cytochrome P450 enzymes, in insects. This inhibition prevents the breakdown and metabolism of pyrethrins, allowing them to remain active for longer durations and increasing their effectiveness against insects. 

Pharmacokinetics: 

Absorption 

pyrethrins are directly absorbed through the skin. Oral absorption is low. PBO is not readily absorbed through the skin and has limited oral absorption. It is primarily used as a topical or surface treatment in combination with pyrethrins. 

Distribution 

pyrethrins are widely distributed throughout the body, with higher concentrations observed in fatty tissues. They are not highly protein-bound and can readily cross cell membranes. 

The distribution of PBO within the body needs to be well-documented. It is expected to have a similar distribution to other lipophilic compounds.  

Metabolism 

pyrethrins are metabolized by enzymes, including esterases and cytochrome P450 enzymes, into inactive metabolites. The primary metabolites are carboxylic acid derivatives. 

PBO is metabolized through oxidation reactions, primarily by cytochrome P450 enzymes. It undergoes hepatic metabolism, resulting in the formation of various metabolites. The specific metabolites and their activities are not extensively studied. 

Elimination and Excretion 

The elimination half-life in humans is relatively short, ranging from a few hours to a few days, depending on the specific compound and the route of exposure. 

The metabolites of PBO are eliminated primarily through urine and feces. 

Adminstartion

Administration: 

pyrethrins and piperonyl butoxide (PBO) are commonly formulated in various insecticidal products, such as sprays, aerosols, shampoos, and lotions. The specific administration instructions may vary depending on the product and its intended use. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: piperonyl butoxide and pyrethrins topical 

Pronounced as: pye-PER-oh-nil-bue-TOX-ide-and-pye-REE-thrins-TOP-i-kal 

Why do we use piperonyl butoxide and pyrethrins topical? 

piperonyl butoxide (PBO) and pyrethrins are commonly used in topical treatments such as insecticides and repellents. They are combined because they have complementary effects that enhance their overall efficacy.