Spinosad topical suspension (0.9%): a new topical treatment for scabies

ABSTRACT

Introduction

Scabies is a highly contagious skin disease caused by the parasitic mite Sarcoptes scabiei. There is no vaccine and for the past 30 years, the first line treatments have been topical permethrin and oral ivermectin. These drugs target mainly the parasite nervous system, killing only the motile stages. As they lack ovicidal activities, repeat treatments are required to achieve complete cure. Incompliance to repeat treatments causing prolonged drug usage has contributed to emerging drug resistances. In addition, they are not appropriate for all patient categories, specifically for infants and young children or pregnant and breast feeding women. Consequently, new single-dose scabicides are urgently needed.

Areas covered

In 2021, spinosad, a drug previously used to treat head lice, was approved by the US FDA as a topical scabies treatment. Here the pharmacology, clinical efficacy, and tolerability of this drug are discussed.

Expert opinion

As the first single-dose scabicide, the formulated 0.9% topical Spinosad solution shows significant efficacy, little systemic absorption, and no serious adverse reactions, making it a promising treatment for classical scabies in patients older than four years.

KEYWORDS:

• scabies
• topical treatment
• single-dose treatment
• spinosad
• efficacy

Article highlights

• Scabies prevalence remains constant, clinical evidence of the limitations of currently available treatments is mounting, and no improved or appropriate new treatment regimen has been developed in the last ~30 years

• Spinosad is the first spinosyn product developed for commercial use

• Spinosad acts on nicotinic acetylcholine receptors and GABA receptors in arthropod muscular and nervous systems, leading to involuntary muscle contraction and paralysis

• Formulated 0.9% spinosad topical suspension is approved by the US FDA as a topical scabies treatment

• Formulated 0.9% spinosad topical suspension shows excellent efficacy, little systemic absorption, and no serious adverse reactions, making it a safe and efficacious treatment for classical scabies in patients older than four years

Declaration of Interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Author contributions

D Fernando and K Fischer have equally contributed to the conception and design of the review article, interpreting the relevant literature, as well as to writing and revising the manuscript.

Additional information

Funding

This manuscript was funded by National Health and Medical Research Council of Australia (APP1154805 and APP1163354).