Topical 5% permethrin cream resulted in higher clinical cure rates compared with oral ivermectin for classic scabies in a recent study, with ivermectin failing to meet noninferiority criteria and permethrin demonstrating statistical superiority at day 28.
In the multicenter, assessor-blinded, cluster randomized SCRATCH trial, researchers enrolled 1,092 adult and pediatric participants from 294 households across 28 French hospitals between January 19, 2016, and December 16, 2021. After exclusion of clusters without valid consent, 507 participants from 142 households in the ivermectin arm and 568 participants from 147 households in the permethrin arm were analyzed.
Index cases were children and adults weighing more than 15 kg with dermoscopy-confirmed classic scabies. Households were randomly assigned in a 1:1 ratio to receive oral ivermectin, 200 µg/kg taken with food, or topical 5% permethrin cream applied head to toe, including hair and genitalia, on day 0 and day 10. Children weighing less than 15 kg received permethrin regardless of assignment. The primary endpoint was cluster-level clinical cure at day 28, defined as resolution of pruritus, burrows, and papules or vesicles in all household members.
In the main cluster-level analysis with multiple imputation, the cure rates were 71.8% in the ivermectin group and 88.5% in the permethrin group, corresponding to a –16.7 percentage point difference.
Secondary analyses were concordant. Among index cases, the cure rates were 76.6% with ivermectin and 91.5% with permethrin, a –14.9 percentage point difference. At the individual participant level, the cure rates were 85.3% vs 94.2%, respectively, a –9.2 percentage point difference. The results were consistent in completer and compliant populations.
Intraclass correlation coefficients were greater in the permethrin group than in the ivermectin group. Post hoc subgroup analyses by cluster size, age group, presence of children weighing less than 15 kg, and number of dermoscopic delta wing signs supported the primary findings.
Cutaneous adverse events potentially related to treatment occurred in 9.9% of index cases treated with ivermectin and 13.6% treated with permethrin. Four serious adverse events were reported but weren't attributed to study treatment.
The trial ended prematurely because of resource limitations, resulting in a smaller-than-planned sample size, although baseline characteristics were balanced between the groups. The findings applied to patients without diffuse eczematization or extensive impetiginization.
“Conversely, the results showed the statistical superiority of permethrin. In decision-making in clinical practice, however, factors such as potential compliance, adherence, and ease of use, as well as molecular and clinical tolerance or resistance to scabicides and the skin condition of patients, should be considered when prescribing treatment for scabies,” noted lead study author Franck Boralevi, Professor of Dermatology in the Department of Paediatric Dermatology at the Hôpital des Enfants at the Groupe Hospitalier Pellegrin as well as Groupe de Recherche de la Société Française de Dermatologie Pédiatrique in France, and colleagues.
The study was funded by the French Ministry of Health and the French Society of Dermatology. Oral ivermectin and topical 5% permethrin were provided free of charge by MSD-Merck and Codexial, respectively. Several investigators reported consultancy roles or participation in trials of related agents. No other relevant financial relationships were disclosed.
Source: The BMJ