Pharmacology Update: Spinosad Topical Suspension 0.9% (Natroba™)
Pharmacology Update
Spinosad Topical Suspension 0.9% (Natroba)
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD. Dr. Elliott is chair, Formulary Committee, Northern California Kaiser Permanente; and Assistant Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Elliott and Chan report no financial relationship to this field of study.
The fda has approved a new topical treatment for head lice infestation. The pediculicide, spinosad, is derived from fermentation of Saccharopolyspora spinosa, a soil actinomycete bacterium. It is marketed by ParaPRO as Natroba.
Indications
Spinosad is indicated for the topical treatment of head lice infestation in patients 4 years of age and older.1
Dosage
A sufficient amount of the suspension should be applied to dry scalp and hair. It should be rinsed off with warm water after 10 minutes.1
The topical suspension contains 9 mg of spinosad per gram.
Potential Advantages
Spinosad has been shown to be more effective than permethrin and is generally effective with one application.1,2 Spinosad is ovicidal and does not require nit combing. Permethrin-resistant head lice may be susceptible to spinosad.3
Potential Disadvantages
Natroba contains benzyl alcohol and, due to the risk of absorption, is not recommended in infants younger than 6 months of age.1
Comments
Spinosad is a nonsynthetic fermentation product of Saccharopolyspora spinosa. Its postulated mechanism of action is neuronal excitation that results in paralysis and death of the head lice.
Its efficacy and safety were evaluated in two identical multicenter, randomized, comparative studies with permethrin (n = 1038). All household members infested were randomized to spinosad 0.9% or permethrin 1%. The youngest subject (6 months of age or older) in each household was considered the primary subject, others were secondary subjects. After the initial treatment, subjects were evaluated on day 7. Those lice-free were evaluated on day 14; those with live lice were given a second treatment. Those given a second treatment were evaluated on day 14 and 21. Efficacy endpoint was the proportion lice-free 14 days after the last treatment. At final assessment, 84.6% (77/91) and 86.7% (72/83) of the primary subjects were lice-free with spinosad compared to 44.9% (40/89) and 42.9% (36/84) for permethrin. For all subjects, 63.8% (155/243) in Study 1 and 86.2% (175/203) in Study 2 required one treatment, while 64.5% (165/256) and 60.3% (129/214) treated with permethrin required two treatments.2 This high percent of success in the spinosad groups was accomplished without nit combing.
Spinosad appears to be well tolerated. Adverse events for spinosad site include erythema (3% vs 7% for permethrin) and ocular edema (2% vs 3% for permethrin).1
Clinical Implications
Head lice infestation is common among preschool and elementary school children. Current therapy is permethrin or pyrethrins when resistance is not expected.4 Spinosad provides a new and highly effective option for the treatment of head lice infestation.
References
1. Natroba Prescribing Information. Magnolia, TX: ParaPRO; January 2011.
2. Stough D, et al. Efficacy and safety of spinosad and permethrin creme rinses for pediculosis capitis (head lice). Pediatrics 2009;124:e389-395.
3. Mougabure Cueto G, et al. Permethrin-resistant head lice (Anoplura: Pediculidae) in Argentina are susceptible to spinosad. J Med Entomol 2006;43:634-635.
4. Frankowski BL, Bocchini JA; and Council on School Health and Committee on Infectious Diseases. Available at: http://aappolicy.aappublications.org/cgi/content/full/pediatrics;126/2/392. Accessed Feb. 13, 2011.
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