Pyrethrins and piperonyl butoxide are used in combination in over-the-counter, topical preparations to treat pediculosis (lice) infestations. Pyrethrins are extracts obtained from flowers of the pyrethrum plant, Chrysanthemum cincerariae folium, which is related to the ragweed plant. Piperonyl butoxide is a piperic acid derivative that has no pesticidal properties of its own. Piperonyl butoxide inhibits the metabolism of pyrethrins by the lice and subsequently enhances the pyrethrins' effect. The addition of piperonyl butoxide may also reduce the development of pyrethrins resistance. Products containing pyrethrins; piperonyl butoxide are indicated for treating infestations caused by Pediculus capitis (head louse), Pediculus corporis (body louse), and Phthirus pubis (pubic or crab louse). Pyrethrins; piperonyl butoxide is not ovicidal, with 20 to 30% of viable eggs remaining after the first application, necessitating a second treatment 7 to 10 days after the first. Unlike some of the other pediculicides, such as permethrin and lindane, pyrethrins; piperonyl butoxide is not effective for the treatment of scabies. Pyrethrins; piperonyl butoxide is considered to be one of the first line agents for the treatment of pediculosis (lice) infestations because of its low risk of toxicity. Like most other topical pediculicides, resistance to pyrethrins; piperonyl butoxide has been reported.
General Administration Information
For storage information, see the specific product information within the How Supplied section.
Route-Specific Administration
Topical Administration
-For topical administration. Do not ingest. Avoid getting into the eyes, nose, mouth, or vagina. Do not apply to the eyelash or eyebrow area; consult a physician if infestation occurs in these areas. A towel or cloth may be used to cover eyes during application.
-Pyrethrins; piperonyl butoxide is available as a gel, lotion, mousse, shampoo, or solution. Any of these formulations can be used on the hair or other affected areas (e.g., skin). When using the mousse, shake the container well before application.
-Apply liberally to dry hair and scalp or other affected areas in a well ventilated area. Apply enough product so that the hair or affected area becomes wet. When using for head lice, apply first to the back of the neck and behind the ears. When applying to the hair, be sure to cover the entire hair shaft, from the roots to the tips.
-Allow the product to remain on the hair or other affected areas for 10 minutes, but no longer. After this 10 minute period, when using the shampoo, use a small amount of warm water to work the shampoo into the hair and scalp or skin until a lather forms. Rinse the hair and/or affected area thoroughly. When using non-shampoo products, thoroughly wash the hair and/or affected areas with warm water and soap or regular shampoo.
-Dry with a clean towel.
-For the proper treatment of lice, nits (eggs) should be removed with a nit comb. All personal headgear, scarfs, coats, and bed linens should be disinfected by machine washing in hot water and drying using the hot cycle of a dryer for at least 20 minutes. Personal articles that cannot be washed may be dry-cleaned, sealed in a plastic bag for 4 weeks, or sprayed with a product specifically designed for this purpose. Personal combs and brushes may be disinfected by soaking in hot water (above 130 degrees F) for 5 to 10 minutes. In addition, for pubic lice, scrub toilet seats frequently.
-Repeat this procedure in 7 to 10 days. Pyrethrins; piperonyl butoxide will not kill all of the louse eggs with the first application.
-The sexual partners of patients being treated for pubic lice should be simultaneously treated to avoid reinfestation.
Pediculosis is often accompanied by pruritus, local edema, and erythema. Pruritus is the most common side effect reported after treatment for pediculosis. Treatment with pyrethrins; piperonyl butoxide may also cause scalp or additional skin irritation. Patients should be informed that this does not mean that the pyrethrins; piperonyl butoxide did not work. Severe adverse reactions with pyrethrins; piperonyl butoxide are not common, given that systemic absorption of pyrethrins; piperonyl butoxide through the skin is minimal. However, the more severe dermatologic adverse reactions following topical administration of pyrethrins; piperonyl butoxide include allergic reaction and skin infection. In 14 clinical trails examining pyrethrins; piperonyl butoxide dermatologic adverse effects included dry, scaly patches, edema, erythema, and pruritus.
Systemic adverse reactions to pyrethrins; piperonyl butoxide following topical administration are extremely rare. Injected, ingested, or inhaled pyrethrins have reportedly caused nausea/vomiting, seizures and death; however, severe poisoning from pyrethrins is rare.
Although rare, exacerbation of asthma including bronchospasm may occur in susceptible patients. Inhalation of pyrethrins has reportedly caused precipitation of asthma symptoms.
Pyrethrins; piperonyl butoxide should be used with caution in patients with a known hypersensitivity to pyrethrins, piperonyl butoxide, chrysanthemums, or ragweed. Some products contain petroleum distillate and may cause problems in patients sensitive to kerosene or petroleum distillate. Products without kerosene or petroleum distillate should be used in these patients.
Pyrethrins; piperonyl butoxide may exacerbate pre-existing skin inflammation.
Products containing pyrethrins; piperonyl butoxide are flammable. Keep away from fire or open flame.
Pyrethrins; piperonyl butoxide is for external use only. Avoid contact with mucus membranes, including the eyes, nose, mouth, and vagina. If ocular exposure occurs, immediately flush the eyes with water. In cases of pediculosis capitis, self-medication is not recommended if infestation of the eyebrows or eyelashes occurs. Do not use pyrethrins; piperonyl butoxide on the eyebrows or eyelashes. A physician should be consulted in these situations.
Apply pyrethrins; piperonyl butoxide in well ventilated area. Avoid excessive inhalation. Pyrethrin-containing products may cause breathing difficulty in susceptible individuals such as persons with asthma.
Pyrethrins; piperonyl butoxide are classified in pregnancy risk category C. This product may be absorbed systemically in small amounts through intact skin; however, problems in humans have not been documented. Guidelines recommend the use of pyrethrins; piperonyl butoxide or permethrin for the treatment of Phthirus pubis (pubic lice) during pregnancy.
It is not known whether topically-applied pyrethrins with piperonyl butoxide is distributed into human milk. However, systemic absorption of the combination after topical application is poor. Guidelines recommend the use of pyrethrins with piperonyl butoxide for pediculosis. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.
Safety and efficacy of pyrethrins; piperonyl butoxide has not been established in neonates, infants, and children < 2 years of age.
Per the manufacturer, this drug has been shown to be active against most strains of the following microorganisms either in vitro and/or in clinical infections: Pediculus capitis, Pediculus corporis, Phthirus pubis
NOTE: The safety and effectiveness in treating clinical infections due to organisms with in vitro data only have not been established in adequate and well-controlled clinical trials.
For the treatment of pediculosis (lice) infestations, including pediculosis capitis, pediculosis corporis, and pediculosis pubis:
-for the treatment of pediculosis capitis (head lice infestation):
Topical dosage:
Adults: Apply liberally to dry hair and scalp or skin. Apply first to back of neck and behind ears. Use enough product to cover entire hair shaft. Allow product to remain on affected areas for 10 minutes, but no longer. Rinse thoroughly and dry affected areas with a clean towel. Repeat application once in 7 to 10 days if live lice are seen. If the first treatment was applied to wet hair, the hair should be rinsed, dried, and then the product should be reapplied in 24 hours. Repeat application on dry hair in 7 to 10 days.
Children and Adolescents 2 to 17 years: Apply liberally to dry hair and scalp or skin. Apply first to back of neck and behind ears. Use enough product to cover entire hair shaft. Allow product to remain on affected areas for 10 minutes, but no longer. Rinse thoroughly and dry affected areas with a clean towel. Repeat application once in 7 to 10 days if live lice are seen. If the first treatment was applied to wet hair, the hair should be rinsed, dried, and then the product should be reapplied in 24 hours. Repeat application on dry hair in 7 to 10 days.
-for the treatment of pediculosis corporis and pediculosis pubis:
Topical dosage:
Adults: Apply liberally to dry hair and skin. Allow product to remain on affected areas for 10 minutes, but no longer. Rinse thoroughly and dry affected areas with a clean towel. Repeat application once in 7 to 10 days if live lice are seen. If the first treatment was applied to wet hair, the hair should be rinsed, dried, and then the product should be reapplied in 24 hours. Repeat application on dry hair in 7 to 10 days.
Children and Adolescents 2 to 17 years: Apply liberally to dry hair and skin. Allow product to remain on affected areas for 10 minutes, but no longer. Rinse thoroughly and dry affected areas with a clean towel. Repeat application once in 7 to 10 days if live lice are seen. If the first treatment was applied to wet hair, the hair should be rinsed, dried, and then the product should be reapplied in 24 hours. Repeat application on dry hair in 7 to 10 days.
Maximum Dosage Limits:
-Adults
2 topical treatments applied 7-10 days apart; if the first treatment is applied to wet hair, repeat treatment should be applied in 24 hours (see Dosage).
-Adolescents
2 topical treatments applied 7-10 days apart; if the first treatment is applied to wet hair, repeat treatment should be applied in 24 hours (see Dosage).
-Children
>= 2 years: 2 topical treatments applied 7-10 days apart; if the first treatment is applied to wet hair, repeat treatment should be applied in 24 hours (see Dosage).
< 2 years: Safety and efficacy have not been established.
-Infants
Safety and efficacy have not been established.
Patients with Hepatic Impairment Dosing
Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.
Patients with Renal Impairment Dosing
Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed.
*non-FDA-approved indication
Benzalkonium Chloride: (Major) Sodium chloride (saline solutions) should not be used to dilute benzalkonium chloride as saline solutions may decrease the antibacterial potency of the antiseptic. Stored tap water should also not be used for dilution since it may contain microorganisms. Resin deionized water may also contain pathogens and it may inactivate benzalkonium chloride.
Benzalkonium Chloride; Benzocaine: (Major) Sodium chloride (saline solutions) should not be used to dilute benzalkonium chloride as saline solutions may decrease the antibacterial potency of the antiseptic. Stored tap water should also not be used for dilution since it may contain microorganisms. Resin deionized water may also contain pathogens and it may inactivate benzalkonium chloride.
Pyrethrins; piperonyl butoxide is used in the treatment of pediculosis infestations. Pyrethrins; piperonyl butoxide does not have activity against scabies.
-Pyrethrins: Pyrethrins are absorbed through the chitinous exoskeleton of arthropods. Once absorbed, pyrethrins block sodium channel repolarization of the arthropod neuron, leading to paralysis and death. Natural pyrethrins are not ovicidal and have no residual activity after rinsing.
-Piperonyl butoxide: Piperonyl butoxide is combined with pyrethrins to inhibit the hydrolytic enzymes responsible for metabolism of pyrethrins in arthropods and to minimize pyrethrin resistance. Piperonyl butoxide has little or no insecticidal activity, but significantly potentiates the insecticidal activity of pyrethrins.
Pharmacokinetics:
Pyrethrins; piperonyl butoxide is applied topically. Detailed human pharmacokinetic data is limited.
-Pyrethrins: Pyrethrins are rapidly, hepatically metabolized via hydrolysis and oxidation. The metabolites are excreted primarily in the urine after conjugation with glucuronide or sulphate. One study of 6 volunteers reported a mean urinary excretion of 1.9% of the applied dose over 7 days. Pyrethrins degrade rapidly when exposed to heat and light.
-Route-Specific Pharmacokinetics
Topical Route
-Pyrethrins: After topical application, percutaneous absorption is minimal; however, more extensive absorption from the gastrointestinal and respiratory tracts has been described.
-Piperonyl butoxide: After topical application, percutaneous absorption is minimal. Volunteer studies with piperonyl butoxide have shown percutaneous absorption of approximately 2% when applied to limbs and 8% when applied to the scalp. More extensive absorption from the gastrointestinal and respiratory tracts has been described. Animal studies suggest that 70% or more of an enterally administered dose of piperonyl butoxide may be absorbed.