Do You Put Spinosad on Wet or Dry Hair? The Proper Application
When treating head lice with spinosad topical suspension, such as the brand-name product Natroba, the manufacturer's instructions explicitly state that the medication must be applied to dry hair. Applying the suspension to wet hair can dilute the active ingredient and reduce its effectiveness, potentially allowing lice and nits (lice eggs) to survive the treatment. Following the instructions precisely is crucial for the medication to work as intended.
Why Dry Hair is Crucial for Efficacy
Spinosad works by direct contact with lice and their eggs. The formulation of the suspension is designed to spread evenly and concentrate the medication on the scalp and hair in its undiluted form. When hair is wet, water can interfere with the product's ability to coat the hair shaft and scalp thoroughly. This dilution effect means that the concentration of spinosad that reaches the lice is lower, which may not be enough to cause the neurological overstimulation necessary to kill them. Ensuring the hair is completely dry before application maximizes the product's killing power, providing a more reliable outcome from a single treatment.
Step-by-Step Spinosad Application Guide
For a successful head lice treatment with spinosad, follow these steps carefully:
- Read the Label: Always begin by reading the patient information and instructions provided with the prescription.
- Shake the Bottle: Shake the bottle of spinosad suspension thoroughly just before use to ensure the medication is evenly mixed.
- Prepare the Hair: Do not wet the hair. Ensure the hair is completely dry before beginning the application.
- Protect the Face: Cover the person’s face and eyes with a towel to prevent accidental contact with the medication. Advise them to keep their eyes closed tightly during application and rinsing.
- Apply to Scalp: Apply the suspension directly to the dry scalp first, where most lice and nits are found. Use enough product to cover the entire scalp area.
- Coat the Hair: After the scalp is covered, work the suspension outwards towards the ends of the hair, ensuring all hair is completely coated. The amount of product needed will vary depending on hair length and thickness.
- Set a Timer: Leave the medication on the hair and scalp for a full 10 minutes. Use a timer or clock to be precise.
- Rinse Carefully: After 10 minutes, rinse the hair and scalp thoroughly with warm water. It is best to do this over a sink to minimize skin exposure to the rinsed-off product.
- Post-Treatment Actions: Wash your hands and the hands of anyone who helped with the application. Shampooing can be done anytime after the treatment.
- Follow-Up: A second treatment should be applied after 7 days if live lice are still visible. Nit combing is not required for effectiveness but may be done to remove dead lice and eggs if desired.
How Spinosad Works
Spinosad is a pediculicide, meaning it is designed to kill lice. Its mode of action is distinct from many other lice treatments. It is derived from a naturally occurring soil bacterium, Saccharopolyspora spinosa, and is classified as a "naturalyte" insecticide.
Unlike traditional organophosphates or carbamates, spinosad acts on the insect's nervous system by targeting specific binding sites on nicotinic acetylcholine receptors. This causes the lice's nerve cells to become overstimulated, leading to continuous muscle contractions, paralysis, and death. Because its mechanism is novel, spinosad has proven effective even in cases where lice have developed resistance to other common insecticides.
Comparison of Common Head Lice Treatments
Understanding the differences between treatment options can help in making an informed decision. Here is a comparison of spinosad with two common over-the-counter alternatives:
| Feature | Spinosad (Natroba) | Permethrin (Nix) | Pyrethrins + Piperonyl Butoxide (RID) |
|---|---|---|---|
| Application | Apply to dry hair. | Apply to damp hair. | Apply to dry hair. |
| Treatment Time | 10 minutes, followed by rinsing. | 10 minutes, followed by rinsing. | 10 minutes, followed by rinsing. |
| Nit Combing | Not required for effectiveness, though can be done. | Typically required to remove nits. | Typically required to remove nits. |
| Second Application | Only if live lice are seen 7 days later. | Often recommended 7-10 days after the first. | Often recommended 7-10 days after the first. |
| Primary Target | Kills live lice and nits. | Primarily kills live lice, less effective on nits. | Primarily kills live lice, less effective on nits. |
| Prescription Status | Prescription only. | Over-the-counter. | Over-the-counter. |
| Best For | Cases of treatment resistance, or for convenience (no nit combing). | First-line treatment for non-resistant infestations. | First-line treatment, often requires thorough combing. |
Side Effects and Safety Information
Spinosad is generally well-tolerated, with the most common side effects being mild irritation at the application site, such as redness of the scalp or eyes. A notable precaution is that spinosad contains benzyl alcohol and is not recommended for use in infants under 6 months of age due to potential risks. Pregnant and breastfeeding individuals should consult a healthcare provider before use. As with any medication, follow the doctor's instructions precisely.
Adjunctive Measures for Lice Management
Effective lice management requires more than just medication. To prevent re-infestation, it is important to treat the environment as well:
- Wash Fabrics: Wash all recently worn clothing, hats, bed linens, and towels in very hot water (130°F or higher) and dry on high heat for at least 20 minutes.
- Clean Personal Items: Soak hairbrushes, combs, and hair clips in hot, soapy water for 5 to 10 minutes.
- Vacuum Thoroughly: Vacuum floors, carpets, and upholstered furniture to remove any stray hairs or lice.
- Seal Non-Washables: Items that cannot be washed, such as stuffed animals or other non-washable toys, can be sealed in a plastic bag for at least 2 weeks to kill any remaining lice or nits.
Conclusion
To answer the question, do you put spinosad on wet or dry hair, the answer is dry. The correct application of spinosad topical suspension to dry hair and scalp for 10 minutes, followed by a rinse, is the prescribed method for effective head lice treatment. This process, along with crucial household cleaning measures, provides a powerful and convenient treatment approach. Always consult a healthcare professional for diagnosis and guidance, especially regarding appropriate usage for specific age groups and potential side effects. A proper understanding of the instructions is the most important factor for success.
Additional resources
For more detailed information, consult the official FDA label for Natroba (spinosad) or the comprehensive drug information available on MedlinePlus.
