Ivermectin for Parasitic Skin Infections of Scabies: A Review of Comparative Clinical Effectiveness, Cost-Effectiveness, and Guidelines

Key Message

Three systematic reviews, one randomized controlled trial, and three guidelines were identified that were relevant to the research questions. There was no conclusive evidence for a difference in clinical effectiveness in terms of cure or complete clearance between oral and topical ivermectin for the treatment of parasitic skin infections of scabies. Topical ivermectin may be associated with lower rates of persistent itching than oral ivermectin. No difference was found between oral and topical ivermectin in the percentage of patients with at least one adverse event.Evidence from the systematic reviews suggested that oral ivermectin was less clinically effective in treating scabies than topical permethrin at one to two weeks following treatment initiation, with no difference between the treatments at later time points. There was also no difference between the treatments in terms of patients with at least one adverse event. Oral ivermectin may be more effective than crotamiton, malathion, benzyl benzoate, and lindane according to one systematic review and more effective than sulphur 10% ointment according to one randomized controlled trial of limited quality. Oral ivermectin may be associated with fewer patients with adverse events than sulfur and more patients with adverse events than synthetic pyrethrins.Topical ivermectin may be more effective than or no different from other scabicides. There was no difference found in clinical effectiveness between topical ivermectin and permethrin in the systematic reviews. According to one systematic review, topical ivermectin may be more effective in treating scabies compared with malathion, lindane, crotamiton, and benzyl benzoate, as well as sulfur at one to two weeks after treatment initiation. Topical permethrin was associated with higher percentages of patients with adverse events compared with synthetic pyrethrins and malathion and lower percentages compared with sulfur.While findings of clinical effectiveness of oral and topical ivermectin were largely consistent among the identified systematic reviews and the randomized controlled trial, there was considerable overlap in primary studies in the systematic reviews and the evidence base consisted mostly of randomized controlled trials of limited quality. Combined with the limited sample sizes in the trials, there is a substantial amount of uncertainty regarding conclusions of clinical effectiveness. With regards to safety, conclusions were also limited by deficiencies in AE reporting. Generalizability to the Canadian treatment setting may be limited due to the locations where the trials were conducted and variability in the treatment regimens used.No relevant studies were identified regarding the comparative cost-effectiveness of oral or topical ivermectin versus scabicides for parasitic skin infections of scabies.Oral ivermectin is recommended by three guidelines for the treatment of scabies and topical ivermectin is recommended as an alternative treatment by one guideline. Oral ivermectin is recommended for the treatment of crusted scabies alone in one guideline and in combination with permethrin cream in another guideline, though these recommendations do not appear to be based on clinical evidence. The applicability of the guideline recommendations to the Canadian setting is unclear as the guidelines were developed for the European and Japanese settings.