Dirlotapide is a microsomal triglyceride transfer protein inhibitor that can be used for weight loss in dogs. Labrador retrievers are known for overeating and obesity. In a dose-response study, 42 dogs, each with a body condition score of 7 or greater out of 9, were given 0.025, 0.5, 0.1, 0.2, or 0.4 mg dirlotapide/kg for 28 days. Dogs in the placebo group gained weight during the trial. In contrast, treated dogs had decreases in body weight, food intake, and fat mass. The mean body weight loss was 1% at 0.1 to 0.4 mg/kg. In a second study, 72 dogs were randomly assigned to 9 treatments: first, they were assigned to 1 of 3 diets containing 5%, 10%, or 15% fat and then within each of those groups they received either placebo, 24 weeks of dirlotapide and 28 weeks of placebo, or 52 weeks of dirlotapide followed by no treatment. Food was offered above maintenance energy requirements. In study B, the initial treatment dose was 0.1 mg/kg. Dogs receiving the drug for 52 weeks had a mean weight loss of 18% to 22% over 24 weeks or 0.8% per week. In contrast, dogs receiving placebo either had a mean weight loss of 4% (5% dietary fat) or mean weight gain (10% to 15% dietary fat). As dogs lost weight, the dose needed to be adjusted. A higher dose of drug was needed in dogs fed the 5% dietary fat diet. The drug was found to be safe over a period of 52 weeks. Lean mass was preserved during the weight-loss period, and posttreatment weight rebound was prevented by a calorie-restricted diet. Study by Pfizer LTD

COMMENTARY: Many Labradors have a body condition score on the heavy side. In fact, in a legal case in England an overweight Lab was taken from his owners and the owners charged with cruelty because it weighed more than 161 pounds. Although the dogs in this study were not that heavy, they did have a mean weight loss of 18% to 22% over a 24-week period. -- The Editors

Evaluation of dirlotapide for sustained weight loss in overweight Labrador retrievers. Gossellin J, Peachey S, Sherington J, et al. J VET PHARMACOL THER 30:55-65, 2007.