Head Lice and the Use of Spinosad

• Published in: Clinical therapeutics 2012, Vol.34 (1), p.14-23
• Main Authors: Villegas, Susan C., PharmD, Breitzka, Robin L., PharmD
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Drug Combinations; Drug Costs; head lice; Health care; Humans; Insecticides; Insecticides - administration & dosage; Insecticides - adverse effects; Insecticides - economics; Insecticides - pharmacokinetics; Insecticides - therapeutic use; Internal Medicine; Lice; Lice Infestations - drug therapy; Lice Infestations - economics; Macrolides - administration & dosage; Macrolides - adverse effects; Macrolides - economics; Macrolides - pharmacokinetics; Macrolides - therapeutic use; Medical Education; Medical sciences; Parasites; pediculosis; Pediculus - drug effects; pediculus humanus capitis; Pharmacology. Drug treatments; Scalp Dermatoses - drug therapy; Scalp Dermatoses - economics; spinosad; Treatment Outcome
• ISSN: 0149-2918; 1879-114X
• DOI: 10.1016/j.clinthera.2011.11.026

Abstract Background Head lice infestations are responsible for social and economic distress. Despite a reported increase in resistance, permethrin 1% is still the first-line treatment of head lice. Alternative topical pediculicidal agents include malathion and benzyl alcohol, but resistance is of growing concern. In 2011, a new pediculicide, spinosad, was introduced. Objective Our aim was to review the clinical pharmacology, efficacy, tolerability, and current place in therapy of spinosad for the treatment of head lice. Methods Pertinent articles and abstracts were identified through searches of MEDLINE/Ebsco and MEDLINE/Ovid from 1948 to September 2011 and International Pharmaceutical Abstracts from 1966 to September 2011. Results Two reports described 3 trials of spinosad used for the treatment of head lice. One study (n = 120) demonstrated efficacy of both spinosad 0.5% and spinosad 1% compared with placebo, with 82.5% and 86.1% of patients free of live lice 14 days after treatment, respectively, compared with 25.6% in the placebo group ( P < 0.001 for each treatment). The difference between the spinosad 0.5% and 1% treatment groups was not significant. Two trials (n = 1038) comparing spinosad 0.9% with permethrin 1% reported greater efficacy for spinosad with absence of live lice 14 days after 1 or 2 treatments for 84.6% and 86.7%, respectively, of primary cases compared with 44.9% and 42.9% with permethrin ( P < 0.001 for both studies). The most common reported adverse events were eye and scalp irritation, but they were not statistically significant ( P = 0.329 and P = 0.395, respectively). Only application-site erythema reactions showed statistical significance, with 6.8% in the permethrin group versus 3.1% in the spinosad group ( P = 0.007). Conclusions Although limited, the available literature suggests that spinosad is an effective and well-tolerated agent for the treatment of head lice. In a time of increasing resistance, spinosad has demonstrated superior performance compared with permethrin. A review of the literature did not identify any studies comparing spinosad to benzyl alcohol 5% or malathion 0.5%.