Field study to investigate the effectiveness and safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio(®) Plus) for the prevention of heartworm disease (Dirofilaria immitis) in client-owned dogs in the USA

BACKGROUND: Dirofilaria immitis, a globally distributed filarial parasite of dogs, is known to cause serious or fatal cardiopulmonary disease. Client-owned dogs were enrolled in a clinical field study in the USA to evaluate the clinical effectiveness and field safety of an orally administered combination investigational product (IP) containing milbemycin oxime and lotilaner (Credelio(®) Plus) as compared to a control product (CP) for the prevention of heartworm disease when administered monthly for 11 consecutive months. METHODS: In this 11-month field study, 319 dogs ≥ 8 weeks old confirmed to be heartworm-negative were enrolled from eight geographically distinct US veterinary clinics, including sites in the southern USA and Mississippi River Valley. The dogs were treated with either the IP combination product at 0.75–1.53 mg/kg milbemycin oxime and 20–41.5 mg/kg lotilaner (n = 159) or the CP (Sentinel(®) Flavor Tabs(®); milbemycin oxime/lufenuron) at the label-recommended dose rate (n = 158.) On day 330, effectiveness was evaluated in each dog using antigen and microfilarial (modified Knott’s) testing to assess the establishment of any patent adult heartworm infections. RESULTS: All dogs treated with the IP combination product and the CP tested negative (100% prevention) for heartworm infection on day 330. The IP combination product tablets containing milbemycin oxime and lotilaner were well tolerated based on the safety assessments in all treated dogs. CONCLUSIONS: This multi-site clinical study using client-owned dogs demonstrated that monthly use of flavored, chewable tablets containing a combination of milbemycin oxime and lotilaner administered orally under end use conditions is safe for dogs. None of the enrolled dogs developed heartworm infections. Eleven consecutive monthly treatments of the IP provided 100% prevention of heartworm disease caused by D. immitis. GRAPHIC ABSTRACT: [Image: see text]