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ANTIPARASITIC PRODUCTS, INSECTICIDES AND REPELLENTS › ECTOPARASITICIDES, INCL. SCABICIDES, INSECTICIDES AND REPELLENTS › ECTOPARASITICIDES, INCL. SCABICIDES › Pyrethrines, incl. synthetic compounds
pyrethrum
P03AC01
Forms & Strengths
- Topical shampoo: Pyrethrins 0.3% with piperonyl butoxide 3%
- Topical solution: Pyrethrins 0.17% to 0.33% with piperonyl butoxide
- Topical foam: Pyrethrins 0.3% with piperonyl butoxide 3%
Adult Dosing
- Pediculosis capitis (head lice): Apply to dry hair until completely wet, massage thoroughly, leave on for 10 minutes, then add warm water, work into a lather, rinse, and comb out nits. Repeat in 7-10 days if live lice are observed.
- Pediculosis pubis (pubic lice): Apply to affected area, leave for 10 minutes, wash thoroughly with warm water and soap.
- Pediculosis corporis (body lice): Treat infested clothing/bedding; topical application to skin if necessary.
Pediatric Dosing
- Infants < 2 years and children: Apply same as adult for pediculosis capitis/pubis, restricted to use in patients aged 2 months and older.
- Neonates < 2 months: Safety and efficacy not established; avoid use due to potential for percutaneous absorption and systemic toxicity.
Indications
- Treatment of infestation by Pediculus humanus capitis (head louse and its nits)
- Treatment of infestation by Phthirus pubis (crab louse)
- Treatment of infestation by Pediculus humanus corporis (body louse)
Mechanism of Action
- Natural pediculicide extracted from Chrysanthemum cinerariifolium flowers
- Acts on the nervous system of invertebrates by prolonging the opening of sodium channels
- Causes delayed repolarization, resulting in paralysis, repetitive nerve discharges, and death of the parasite
- Combined with piperonyl butoxide to inhibit insect cytochrome P450 enzymes, preventing breakdown of pyrethrins
Contraindications
- Hypersensitivity to pyrethrins, pyrethroids, or chrysanthemum-based extracts
- Known allergy to ragweed (cross-reactivity possible)
- Application to broken, inflamed, or infected skin
Adverse Reactions
- Local skin irritation, burning, or stinging at application site
- Erythema and edema of the scalp or skin
- Contact dermatitis and pruritus
- Rare: anaphylaxis or acute asthma exacerbation in sensitive individuals
Drug Interactions
- No significant systemic drug interactions documented due to minimal percutaneous absorption
- Potential additive skin irritation when used concurrently with other topical anti-lice agents or drying alcohols
Curated Content: Needs Vetting Before Put to Clinical Use