Pharmacokinetics and metabolism of eprinomectin in cats when administered in a novel topical combination of fipronil, (S)-methoprene, eprinomectin and praziquantel.

Abstract

Four studies were conducted to determine the pharmacokinetic characteristics and in vitro metabolism of eprinomectin, a semi-synthetic avermectin, in cats. Pharmacokinetic parameters including bioavailability of eprinomectin were determined in a parallel study design comprised of one group of eight cats which were treated once topically at 0.12 mL/kg bodyweight with BROADLINE(®), a novel combination product (fipronil 8.3% (w/v), (S)-methoprene 10% (w/v), eprinomectin 0.4% (w/v) and praziquantel 8.3% (w/v)), delivering a dose of 0.5mg eprinomectin per kg body weight, and a group of six cats which received 0.4% (w/v) eprinomectin at 0.4 mg/kg bodyweight once by intravenous injection. For cats treated by topical application, the average eprinomectin (B1a component) maximum plasma concentration (Cmax) was 20 ng/mL. The maximum concentrations were reached 24h after dosing in the majority of the animals (six of eight cats). The average terminal half-life was 114 h due to slow absorption ('flip-flop' kinetics). Following intravenous administration the average Cmax was 503 ng/mL at 5 min post-dose, and the mean elimination half-life was 23 h. Eprinomectin was widely distributed with a mean volume of distribution of 2,390 mL/kg, and the clearance rate was 81 mL/h/kg. Mean areas under the plasma concentration versus time curves extrapolated to infinity were 2,100 ngh/mL and 5,160 ngh/mL for the topical and intravenous doses, respectively. Topical eprinomectin was absorbed with an average absolute bioavailability of 31%. In a second parallel design study, the dose proportionality of eprinomectin after single topical administration of BROADLINE(®) was studied. Four groups of eight cats each were treated once topically with 0.5, 1, 2 or 5 times the minimum recommended dose of the combination, 0.12 mL/kg bodyweight. Based on comparison of areas under the plasma concentration versus time curves from the time of dosing to the last time point at which eprinomectin B1a was quantified, and Cmax, dose proportionality was established. In addition, the metabolic pathway of eprinomectin using cat liver microsomes, and plasma protein binding using cat, rat, and dog plasma were studied in vitro. Results of the analyses of eprinomectin B1a described here showed that it is metabolically stable and highly protein bound (>99%), and thus likely to be, as with other species, excreted mainly as unchanged parent drug in the feces of cats.

• Authors: Valerie Kvaternick, Michael Kellermann, Martin Knaus, Steffen Rehbein, Joseph Rosentel
• Journal: Veterinary parasitology (Vet Parasitol) Vol. 202 Issue 1-2 Pg. 2-9 (Apr 28 2014) ISSN: 1873-2550 [Electronic] Netherlands
• PMID: 24703069 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Chemical References

• Antiparasitic Agents
• Drug Combinations
• Pyrazoles
• Praziquantel
• Ivermectin
• eprinomectin
• Methoprene
• fipronil

Topics

• Administration, Topical
• Animals
• Antiparasitic Agents (administration & dosage, blood, metabolism, pharmacokinetics)
• Cat Diseases (drug therapy)
• Cats
• Drug Combinations
• Female
• Ivermectin (administration & dosage, analogs & derivatives, blood, metabolism, pharmacokinetics)
• Male
• Methoprene (administration & dosage)
• Parasitic Diseases, Animal (drug therapy)
• Praziquantel (administration & dosage)
• Pyrazoles (administration & dosage)
• Random Allocation