Spinosad (Natroba)

How Medicare covers it

Part D (forms used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

Head lice infestations in adults and children 6 months of age and older, and scabies infestations in adults and children 4 years of age and older. Brand name Natroba. It is applied to the skin, scalp, and hair only.

What it is for, in depth

Natroba (spinosad) is a prescription liquid used on the skin to kill head lice in adults and children 6 months and older, and to treat scabies, which is caused by tiny mites in the skin, in adults and children 4 years and older. It is a direct, one-time treatment put right where the lice or mites live, rather than a pill, and for lice it is used as part of an overall program that also includes hot-water washing of recently worn clothing, bedding, towels, combs, and brushes. For lice it stays on dry hair and scalp for 10 minutes before being rinsed off, and a second treatment is used only if live lice are seen 7 days later; for scabies it covers the body from neck to toes and stays on at least 6 hours. It comes as a 0.9% topical suspension (9 mg of spinosad per gram) in a 120 mL bottle.

How it works

Spinosad causes neuronal excitation in insects. After periods of hyperexcitation, lice and scabies mites become paralyzed and die. Natroba is described in the label as a pediculicide and scabicide, and spinosad is not absorbed into the bloodstream in measurable amounts after use on the skin.

How it is taken

For head lice: shake the bottle well, apply enough to cover the dry scalp and then dry hair (up to one 120 mL bottle depending on hair length), leave on for 10 minutes, then rinse well with warm water; if live lice are seen 7 days after the first treatment, apply a second treatment. For scabies: apply enough to completely cover the body from the neck to the toes, including the soles of the feet (and the scalp, hairline, temples, and forehead if balding), let it dry for 10 minutes before getting dressed, and leave it on the skin for at least 6 hours before showering or bathing. For topical use only — not for oral, eye, or intravaginal use; avoid contact with the eyes and wash hands after use. Children should have it applied only under direct adult supervision.

Common side effects

For head lice, the most common side effects (at least 1% in trials) were redness where it was applied (3%), redness of the eyes (2%), and irritation where it was applied (1%); less common effects included dryness or peeling where applied, hair loss, and dry skin. For scabies, the effects in at least 1% were irritation where applied (3%, including pain and burning) and dry skin (2%).

Serious warnings

The label's only warning is benzyl alcohol toxicity: Natroba contains benzyl alcohol and is not approved for use in newborns and infants below the age of 6 months, because body-wide exposure to benzyl alcohol given by vein has been linked to serious reactions and death in newborns and low birth-weight infants. The label lists no contraindications.

Who should be careful

Do not use in infants below 6 months of age for head lice, or in children below 4 years of age for scabies. People with skin conditions or sensitivities should tell their clinician before use. Spinosad is not absorbed through the skin, so use in pregnancy is not expected to expose the unborn baby to the drug; breastfeeding women should wash Natroba off the breast with soap and water before breastfeeding so the baby does not touch it directly.

Major interactions

The Natroba label has no drug interactions section and lists no drug interactions. This fits with the label's pharmacokinetic findings: after a single topical treatment, spinosad levels in the blood were below the limit of measurement in all samples tested.

Cost and saving notes

This drug is usually covered under Medicare Part D. If your cost is high, ask your plan about a tier exception. If you have limited income, the Extra Help (Low-Income Subsidy) program can lower your Part D premiums and drug costs. In 2027, your total yearly out-of-pocket spending on Part D drugs is capped at $2,400, and you can ask your plan to spread those costs out in monthly payments through the Medicare Prescription Payment Plan.

Why it is in its tier

Spinosad (Natroba) sits on Tier 4 in 100.0% of the plans that list it (70 of 70 listing plans). Tier 4 is the non-preferred tier — higher copays or coinsurance. The data-visible drivers: It is a generic product, and the CMS dashboard puts its average Part D spending at about $402 per beneficiary for 2024 — a relatively low-cost drug, which matches where plans place it. Only 1.27% of Part D plans list it at all, so many readers will find their plan does not list it and covers a similar drug instead. The tier shown is the most common one; individual plans vary.

Sources

• NATROBA (SPINOSAD) SUSPENSION [CIPHER PHARMACEUTICALS INC.] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus Drug Information

What official patient guides say

Spinosad is not a daily medicine; it is a one-time treatment you put on the skin, scalp, and hair, with no food rules and your normal diet unchanged. Shake the bottle well first. For head lice, apply it to dry scalp and then dry hair until everything is covered, use a timer to leave it on for 10 minutes, then rinse it out with warm water in a sink, wash your hands, and wash recently used clothes, bedding, hats, and towels in hot water. Check again in a week: a second treatment is used only if live lice are still seen 7 days after the first. For scabies, rub it over the whole body from the neck to the soles of the feet, including skin folds and under the nails, let it dry for 10 minutes before getting dressed, and leave it on for at least 6 hours before showering or bathing. There is no missed-dose rule, because it is a single treatment. Store the bottle at room temperature, tightly closed, away from heat and moisture, and out of the reach of children. Redness or irritation where it was applied is the most common thing to expect.

Source: MedlinePlus Drug Information

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is 2.01315 per unit (SPINOSAD 0.9% TOPICAL SUSP) — about nan for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 70 list Spinosad (Natroba) — 1.3% of plans. Most of those plans put it on Tier 4: 70 plans, 100% of the plans that list it. Every plan that lists it puts it on Tier 4. For example: UPMC for Life PPO Rx Enhanced (PPO) puts it on Tier 4; Healthy Mississippi Preferred (PPO) puts it on Tier 4; Healthy Mississippi Dual Advantage (PPO D-SNP) puts it on Tier 4. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan';s deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.