Comprehensive medication guide to Stop Lice Maximum Strength including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$0 with FSA/HSA (eligible OTC expense); traditionally not covered by commercial insurance without a prescription, though some Medicaid plans cover it when prescribed. Use FSA/HSA card at the register for maximum savings.
Estimated Cash Pricing
$8–$20 per bottle at most pharmacies; store-brand generics with the same active ingredients (pyrethrins 0.33% + piperonyl butoxide 4%) may cost 30–50% less. Two bottles required per person (two treatments, 7–10 days apart).
Medfinder Findability Score
72/100
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Stop Lice Maximum Strength is an over-the-counter (OTC) pediculicide shampoo used to treat head lice, body lice, and pubic lice in adults and children 2 years of age and older. It is available without a prescription at pharmacies, grocery stores, and online retailers.
The active ingredients are pyrethrum extract (equivalent to 0.33% pyrethrins) and piperonyl butoxide 4%. Pyrethrins are natural insecticides derived from chrysanthemum flowers; piperonyl butoxide is a synergist that enhances pyrethrin effectiveness by blocking lice enzymes that would otherwise break down the active compound. This combination is the same formula found in other well-known OTC lice treatments including RID, A-200, and Pronto.
Treatment requires two applications: one on Day 1 and a second 7–10 days later, because pyrethrins kill live lice but not unhatched eggs (nits). A fine-toothed nit comb is typically included to remove dead lice and eggs after treatment.
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Pyrethrins kill lice by targeting voltage-gated sodium channels in the insect's nerve cells. Normally, these channels open briefly to transmit electrical signals and then close. Pyrethrins bind to these channels and prevent them from closing, causing continuous, uncontrolled nerve firing that results in muscle spasms, paralysis, and death of the louse.
Piperonyl butoxide blocks the enzymes lice use to detoxify pyrethrins, allowing more of the active compound to reach the sodium channel target. This synergistic combination makes the formula more effective than pyrethrins alone. Human nervous systems are far less sensitive to pyrethrins than insect nervous systems, and the minimal systemic absorption from a 10-minute topical application makes this treatment safe when used as directed.
A critical limitation: approximately 77% of head lice worldwide carry knockdown resistance (kdr) gene mutations that alter the sodium channel structure and reduce pyrethrin effectiveness. In areas with high resistance rates, OTC pyrethrin treatments may not be effective. Signs of resistance include live lice still moving 24 hours after a correctly applied treatment.
Pyrethrin 0.33% / Piperonyl Butoxide 4% — shampoo (topical)
Apply to dry hair, leave 10 minutes, rinse. Repeat in 7–10 days.
Stop Lice Maximum Strength is not in a national shortage as of 2026. However, finding this specific brand at a specific pharmacy near you may take some effort. Not every pharmacy chain stocks this brand, and seasonal demand spikes — especially during the back-to-school period in August and September — can clear shelves at individual store locations.
The good news: if Stop Lice Maximum Strength is not on the shelf, any OTC lice shampoo with the same active ingredients — pyrethrins 0.33% and piperonyl butoxide 4% — will work identically. Store-brand versions at major pharmacy chains contain the same formula at a lower price.
If you need help finding Stop Lice Maximum Strength in stock at a pharmacy near you, medfinder calls pharmacies in your area and texts you which ones currently have your medication available — so you can go directly to where it's stocked.
Stop Lice Maximum Strength is an OTC product and does not require a prescription. Any adult can purchase it without seeing a healthcare provider. However, if OTC treatment fails and a prescription alternative is needed, any of the following licensed providers can prescribe stronger lice treatments:
Prescription lice treatments (spinosad, ivermectin lotion, benzyl alcohol) are not controlled substances and can be prescribed via telehealth. Many platforms — including Teladoc and MDLive — see lice cases and can send prescriptions to your local pharmacy the same day.
No. Stop Lice Maximum Strength is not a controlled substance. It has no DEA scheduling designation and does not require a prescription. It is available over the counter (OTC) at pharmacies, grocery stores, and online without any special authorization.
There are no refill restrictions, quantity limits from DEA regulations, or special dispensing requirements for this product. Any adult can purchase it without a prescription, and there is no limit on how many bottles can be purchased at one time.
Most people tolerate Stop Lice Maximum Strength without significant problems. Common side effects that typically resolve on their own include:
Serious side effects (rare — seek emergency care immediately):
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Nix (Permethrin 1%)
OTC synthetic pyrethroid; applied to damp hair; approved for children 2+ months; similar resistance challenges.
Spinosad (Natroba)
Prescription; kills live lice AND eggs; effective against resistant lice; single application usually sufficient.
Ivermectin Lotion (Sklice)
Prescription; single application to dry hair; no nit combing required; approved for children 6+ months.
Benzyl Alcohol 5% (Ulesfia)
Prescription; kills by asphyxiation — no resistance possible; two applications 7 days apart; approved for children 6+ months.
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Other Lice Treatments
moderateDo not use two different lice medications simultaneously. May increase scalp irritation without improving efficacy.
Hair Conditioner
moderateUsing conditioner before application significantly reduces effectiveness. Do not use conditioner or combination shampoo-conditioner before applying.
Ragweed / Chrysanthemum Allergy (Contraindication)
majorPyrethrins are derived from chrysanthemums. Cross-reactivity with ragweed can cause breathing difficulty or allergic reactions. Do not use if allergic.
Stop Lice Maximum Strength is an effective and accessible OTC treatment for head lice when used correctly — with two applications 7–10 days apart, thorough nit combing, and simultaneous treatment of all household members with confirmed infestations. It is widely available at pharmacies and online, is not a controlled substance, and is eligible for FSA/HSA reimbursement.
The most important caveat in 2026 is pyrethroid resistance. Approximately 77% of lice worldwide carry resistance mutations, which can significantly reduce OTC pyrethrin efficacy. If live lice are still present 24 hours after a correctly applied treatment, contact a healthcare provider for a prescription alternative such as spinosad (Natroba) or ivermectin lotion (Sklice).
If you're having trouble finding Stop Lice Maximum Strength or a prescription alternative at a pharmacy near you, medfinder can call pharmacies on your behalf and text you which ones currently have your medication in stock — eliminating the guesswork and saving you time when you need treatment fast.
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Our medication guides are researched and written to help patients make informed decisions. All content is reviewed for accuracy and updated regularly. Learn more about our standards
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