Pharmacotherapy of ectoparasitic infections

Epizoonoses such as scabies, lice and cimicosis are common, vexing disorders that occur worldwide. Historically, many treatment modalities have been employed in the management of these disorders, and most of the drugs described in this review are of historical interest and no longer recommended or in widespread use because of their wide spectrum of adverse effects. More recently, reports documenting resistance against various antiectoparasite drugs, complicated and severe courses of the diseases, and adverse effects of drug therapy have prompted the development of new treatment strategies and drugs for optimal disease management. Because the strategies currently recommended for the treatment of ectoparasites differ worldwide, this review proposes a rational approach to selecting the best therapeutic agent by comparing the pharmacokinetics, pharmacodynamics, drug efficacy and adverse effects. A literature search of the currently Internet accessible libraries PubMed, Medline and Ideal library, of citations of articles found there, and from communications with the Federal Institute for Drugs and Medical Devices, Germany, was conducted based on this approach. One major observation of this literature search is that permethrin is the treatment of choice for lice and scabies in the US and in Great Britain, whereas lindane is still recommended for scabies in most other European countries because of its longer-standing record of effectiveness. Although permethrin has not yet been proven to be more effective than lindane in treating infections with these ectoparasites, it currently appears to have the best efficacy versus safety profile of topical treatments for scabies and lice. Ivermectin is a newer oral drug for the treatment of ectoparasites, which has been used with great success in the treatment of onchocercosis and other endoparasites. Although ivermectin appears to be a promising drug, its role in the treatment of ectoparasitic infections will be clarified as more study data become available. Finally, it is important to emphasise the clinical aspects of ectoparasite therapy and that providing the patient with optimal instructions on the use of topical therapeutics is of great importance in avoiding adverse effects and assuring complete removal of the ectoparasite, thereby avoiding the development of drug-resistance.