Scabies: Molecular Perspectives and Therapeutic Implications in the Face of Emerging Drug Resistance

Kate E. Mounsey; Deborah C. Holt; James McCarthy; Bart J. Currie; Shelley F. Walton


Future Microbiol. 2008;3(1):57-66. 

In This Article


Although scabies is an ancient disease, treatment options remain limited. Over recent years permethrin has emerged as the topical agent of choice owing to its efficacy and high tolerability, although there are concerns regarding emerging tolerance. Despite its promise, there are still several unresolved issues regarding the use of oral ivermectin for both ordinary and crusted scabies.

Importantly, the uncertainty regarding therapeutic ivermectin and permethrin concentrations in situ should also be examined if we are to fully understand their pharmacodynamics. In humans with ordinary scabies, levels of ivermectin in skin reached peak concentration within 8 h and declined markedly after 24 h,[65] suggesting selective pressure would remain low. The opposite may be true in crusted scabies, where sub-therapeutic drug concentrations in hyperkeratotic skin crusts may occur for prolonged periods, favoring selection for drug-resistant mites, particularly under a multiple-dose regimen.

Improved surveillance for emerging resistance to acaricides is critical. In addition, defining the genetic basis of resistance will facilitate the development of molecular approaches to enable more effective monitoring and control for the spread of resistance in scabies endemic communities. In the meantime, continued in vitro testing remains an important adjunct to routine clinical practice for individual patients and during community mass treatment initiatives to ensure the ongoing successful treatment of scabies.


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