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Data from a recent study found spinosad (Natroba) to be a safe and effective treatment option for scabies.

A suspension of spinosad at 0.9% was approved by the FDA last year for the treatment of scabies infestations in patients 4 years of age and older. It was also previously approved for the topical treatment of head lice.

Previously, other scabies treatments posed a range of potential problems including resistance, presenting a need for effective new therapies. In this study, 78.1% of the subjects who received spinosad were completely cured by day 28, compared with 39.6% of those in the control group. Further, no significant safety issues or adverse events were identified.

The report was published in the . The following excerpts from the text have been edited for length and clarity.

What were the existing scabies treatments before spinosad, and what were the associated problems?

Topical treatments for scabies historically included products containing permethrin, lindane, and crotamiton. Other prescription therapies including topical malathion and oral and topical ivermectin were also sometimes used off-label.

Each option carried substantial disadvantages, including a limited availability of efficacy data and potential risks such as resistance, exacerbation of skin irritation, and contraindications in children and pregnant women.

There are no approved over-the-counter treatments for scabies, although soaps and creams containing sulfur are often used. However, the efficacy of sulfur for the treatment of scabies has not been rigorously established.

What was the study designed to ascertain?

Prior to this study, spinosad had not been evaluated for the treatment of scabies. To evaluate spinosad for the treatment of scabies, two controlled, phase-3 clinical studies were conducted.

In these studies, patients with active scabies infestations and members of their households all were treated with either a suspension of spinosad or a control drug.

What were the study's key findings on efficacy?

Spinosad at 0.9% performed better than control in the eradication of scabies when applied as a single topical treatment from the neck down and when left on the skin for at least six hours prior to being washed off.

Efficacy was confirmed by both observing reductions in relevant signs and symptoms and in the eradication of mites.

In general, spinosad represents a new scabies treatment option for clinicians and patients who otherwise have few other choices. It is an effective treatment because of its ability to reach mites in the stratum corneum, where they feed and reproduce.

What about spinosad's safety profile?

Spinosad appeared to be well tolerated and did not raise safety concerns.

None of the events experienced in the spinosad group (n=306) occurred in ≥1% of the patients. The only individual events experienced by more than one patient were abdominal pain, back pain, burning sensation, cough, headache, neck pain, and decreased weight, each of which occurred in two patients (0.8%).

The only events considered by the investigator to be directly related to spinosad were burning sensation (two subjects [0.7%]) and dry skin (one subject [0.3%]). Both events occurred shortly after study drug application.

IMPLICATIONS FOR PRACTICE:

• Spinosad 0.9% was found to be an effective treatment option for scabies in patients four years of age and older.
• Spinosad, an insecticide, was also shown to be safe and well tolerated.
• Other options for scabies treatments present issues of resistance and significant side effects.