Long-term and acute safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio ® Plus) in juvenile and adult dogs

Background The combination of milbemycin oxime (MO) and lotilaner (Credelio ® Plus) is a novel systemic endectocide that provides month-long effectiveness in dogs after a single oral treatment. The safety of Credelio ® Plus flavored chewable tablets was investigated in three target animal safety studies. Two studies (one in juveniles and one in adults) evaluated the long-term safety, and one study evaluated the acute safety of the product when administered orally at the upper end of the recommended dose range (0.75–1.53 mg/kg MO and 20–41 mg/kg lotilaner) and multiples of this dose. Methods The objectives of these studies were to determine the long-term and acute safety of MO and lotilaner flavored chewable tablets in healthy dogs. All three studies were randomized, blinded, parallel-group design studies in healthy Beagle dogs. In each of the two long-term studies, 32 dogs were randomized among four groups to untreated controls or to treated groups at target doses of 1X, 3X, or 5X. Treatment was administered on seven (adult dogs) or nine (juvenile dogs) occasions with dosing every 4 weeks. In the acute study, 48 dogs were randomized among four groups to untreated controls or to treated groups at 1X, 3X, or 6X. In all three studies, the control group was administered placebo tablets. All dogs were fed 30 to 45 min prior to treatment and the assessment of safety was based on health observations, complete physical/neurological examinations, and food consumption. For the long-term safety studies, safety assessments also included clinical pathology evaluations (hematology, clinical chemistry and urinalysis), body weight, pharmacokinetic blood collections, and macroscopic and microscopic examinations of collected tissues. Results MO and lotilaner did not induce any treatment-related adverse effects based on health observations, physical/neurological examinations, or food consumption in the long-term or acute studies. Additionally, in the long-term studies, MO and lotilaner did not induce any treatment-related effects on clinical pathology, body weight, and macroscopic and microscopic examinations. Conclusions These three studies demonstrate that Credelio ® Plus has a wide safety margin when administered at monthly intervals to puppies and dogs at the high end of the commercial dose band. Graphical Abstract