Safety of Credelio Quattro in dogs with adult heartworms

Abstract

BACKGROUND: Credelio Quattro (lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets) is a novel endectocide for monthly oral administration in dogs. The safety of Credelio Quattro was investigated in dogs with pre-existing patent heartworm (Dirofilaria immitis) infections. Heartworm preventive products are tested in heartworm-positive dogs as rapid microfilarial and adult worm death can lead to serious clinical reactions, including death. METHODS: This was a gender-stratified, randomized, placebo-controlled, blinded, parallel group design study. Prior to study, dogs were surgically implanted with 10 male and 10 female adult D. immitis worms (Georgia III isolate). After confirming a patent infection, dogs were randomized into three groups (placebo control, 1×, or 3× the maximum recommended labeled dose of Credelio Quattro) consisting of eight dogs each. Treatment was administered on three consecutive monthly occasions. The assessment of safety was based on body weight, physical examinations, clinical observations on the days of dosing, general health observations, microfilariae (MF) counts, and D. immitis antigen testing. On the last day of study, the heart, lungs, and pleural and peritoneal cavities were examined for adult D. immitis worms. RESULTS: Credelio Quattro was well tolerated. Emesis occurred in the 3× group only. Diarrhea was observed in all groups at various times throughout the study. Owing to the timing of events relative to dosing, emesis and diarrhea were possibly related to treatment; however, all dogs recovered quickly and without treatment. No signs of avermectin toxicity or hypersensitivity reactions were observed in any dog. Compared with control, Credelio Quattro reduced the concentration of circulating MF on study day 1 by 38.8% for the 1× group and significantly reduced MF by 73.3% for the 3× group. MF reduction remained significant for both groups at all subsequent time points. CONCLUSIONS: Credelio Quattro, when administered at 1× and 3× the maximum recommended label dose, was well tolerated following three consecutive monthly administrations to heartworm-positive dogs. Although Credelio Quattro caused a rapid reduction in microfilaria counts, no adverse effects related to microfilaria reduction were observed, and there was no effect on adult worms in this study.