title: Degradation rate of praziquantel and fenbendazole in rainbow trout following oral administration.
abstract: OBJECTIVE
  The aim of this study was to evaluate and compare the rate of degradation and elimination of praziquantel and fenbendazole antiparasitics following oral administration to salmonids. In addition, we determine whether the length of the legal withdrawal period is sufficient for complete elimination of antiparasitic residue from the body. The use of these drugs in fish is currently considered off-label and data on degradation are not available for rainbow trout.
  
  
  METHODS
  The model species for this experiment was the rainbow trout (Oncorhynchus mykiss) and praziquantel and fenbendazole were chosen for experimental therapy. Both drugs were administered into the gastrointestinal tract using a stomach tube. Concentrations of fenbendazole and praziquantel were established through high performance liquid chromatography-tandem mass spectrometry.
  
  
  RESULTS
  Our results show that concentrations of praziquantel and fenbendazole reach their maximum in the body within 24 hours of administration, with concentrations dropping sharply over the following 24 hours. With one exception, when trace amounts of both substances were found in blood plasma, the drugs were completely degraded and eliminated from the body by the end of the experiment (corresponding to 497.6 degree days).
  
  
  CONCLUSIONS
  Praziquantel and fenbendazole both show a high rate of degradation and elimination from fish. As both substances were eliminated from the body within the required withdrawal period (i.e. within 500 degree days) they can be safely used based on current knowledge of their therapeutic effect for treating helminth infections.
authors.affiliation: Department of Ecology and Diseases of Game, Fish and Bees, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Soukupova-Markova
authors.affiliation: Department of Veterinary Public Health and Toxicology, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Veronika
authors.initials: V
authors.lastname: Doubkova
authors.affiliation: Department of Veterinary Public Health and Toxicology, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Marsalek
authors.affiliation: Department of Veterinary Public Health and Toxicology, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Svobodova
authors.affiliation: Department of Ecology and Diseases of Game, Fish and Bees, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Ivana
authors.initials: I
authors.lastname: Papezikova
authors.affiliation: Department of Zoology, Fisheries, Hydrobiology and Apiculture, Faculty of Agronomy, Mendel University, Brno, Czech Republic.
authors.forename: Stepan
authors.initials: S
authors.lastname: Lang
authors.affiliation: Department of Ecology and Diseases of Game, Fish and Bees, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Navratil
authors.affiliation: Department of Ecology and Diseases of Game, Fish and Bees, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic.
authors.forename: Miroslava
authors.initials: M
authors.lastname: Palikova
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000871:Anthelmintics / Q000493:pharmacokinetics; D000969:Antinematodal Agents / Q000493:pharmacokinetics*; D002853:Chromatography, Liquid; D005273:Fenbendazole / Q000493:pharmacokinetics*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D011223:Praziquantel / Q000493:pharmacokinetics*
chemical_list: D000871:Anthelmintics; D000969:Antinematodal Agents; D005273:Fenbendazole; D011223:Praziquantel