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Pseudoresistance to permethrin in scabies
Stefano Veraldi1, Rossana Schianchi2, Martina Silvio1
1Department of Pathophysiology and Transplantation, Università degli Studi, Foundation IRCCS, Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
Abstract:
Reports of permethrin resistance of Sarcoptes scabiei var. hominis are emerging. We propose that this may be pseudoresistance. The resistance is due to inadequate counselling by physicians, incorrect treatment (insufficient quantity of permethrin; too short length of treatment), and poor adherence and compliance by patients. Other reasons include single application of permethrin, suggestion to apply the drug for 6-8 hours, failed application on subungual folds, irritant contact dermatitis, in particular on genitals, for which some patients stop the treatment, and unexplainable use of permethrin in post-scabies prurigo. Thus, we believe that several cases of resistance to permethrin are actually cases of pseudoresistance.
Insights
Emerging permethrin resistance in scabies may be pseudoresistance. Factors like poor patient adherence and incorrect treatment application by physicians contribute to treatment failure, not true drug resistance.
Area of Science:
- Dermatology
- Parasitology
- Pharmacology
Background:
- Reports of permethrin resistance in *Sarcoptes scabiei var. hominis* infections are increasing.
- This phenomenon necessitates an investigation into potential underlying causes beyond true drug resistance.
Discussion:
- Physician-related factors include inadequate patient counseling and incorrect treatment prescribing (e.g., insufficient quantity, duration).
- Patient-related factors involve poor adherence, non-compliance, and improper application techniques (e.g., missing subungual folds).
- Other contributing factors include irritant contact dermatitis leading to treatment cessation and inappropriate use in post-scabies prurigo.
Key Insights:
- Many reported cases of permethrin resistance are likely pseudoresistance, stemming from application and adherence issues.
- Correcting counseling, treatment protocols, and patient education can potentially improve therapeutic outcomes.
Outlook:
- Further research should focus on standardizing treatment guidelines and improving patient education to address pseudoresistance.
- Enhanced understanding and management of pseudoresistance are crucial for effective scabies control programs.
