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Free Content Treatment of MDR1 Mutant Dogs with Macrocyclic Lactones

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P-glycoprotein, encoded by the multidrug resistance gene MDR1, is an ATP-driven drug efflux pump which is highly expressed at the blood-brain barrier of vertebrates. Drug efflux of macrocyclic lactones by P-glycoprotein is highly relevant for the therapeutic safety of macrocyclic lactones, as thereby GABA-gated chloride channels, which are confined to the central nervous system in vertebrates, are protected from high drug concentrations that otherwise would induce neurological toxicity. A 4-bp deletion mutation exists in the MDR1 gene of many dog breeds such as the Collie and the Australian Shepherd, which results in the expression of a non-functional P-glycoprotein and is associated with multiple drug sensitivity. Accordingly, dogs with homozygous MDR1 mutation are in general prone to neurotoxicity by macrocyclic lactones due to their increased brain penetration. Nevertheless, treatment of these dogs with macrocyclic lactones does not inevitably result in neurological symptoms, since, the safety of treatment highly depends on the treatment indication, dosage, route of application, and the individual compound used as outlined in this review. Whereas all available macrocyclic lactones can safely be administered to MDR1 mutant dogs at doses usually used for heartworm prevention, these dogs will experience neurological toxicity following a high dose regimen which is common for mange treatment in dogs. Here, we review and discuss the neurotoxicological potential of different macrocyclic lactones as well as their treatment options in MDR1 mutant dogs.

Keywords: Dog; MDR1; P-glycoprotein; ivermectin; ivermectin-sensitive Collie; milbemycin oxime; moxidectin; pharmacogenetics

Document Type: Research Article

Affiliations: Institute of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Justus Liebig University of Giessen, Frankfurter Str. 107, 35392 Giessen, Germany.

Publication date: May 1, 2012

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  • Current Pharmaceutical Biotechnology aims to cover all the latest and outstanding developments in Pharmaceutical Biotechnology. Each issue of the journal contains a series of timely in-depth reviews written by leaders in the field covering a range of current topics in both pre-clinical and clinical areas of Pharmaceutical Biotechnology. Current Pharmaceutical Biotechnology is an essential journal for academic, clinical, government and pharmaceutical scientists who wish to be kept informed and up-to-date with the latest and most important developments.
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