Platelet aggregometry testing during aspirin or clopidogrel treatment and measurement of clopidogrel metabolite concentrations in dogs with protein-losing nephropathy.

backgroundDogs with protein-losing nephropathy (PLN) are treated with antiplatelet drugs for thromboprophylaxis but no standardized method exists to measure drug response. It is also unknown if clopidogrel metabolite concentrations [CM] differ between healthy and PLN dogs.

objectivesAssess response to aspirin or clopidogrel in PLN dogs using platelet aggregometry (PA) and compare [CM] between healthy and PLN dogs. ANIMALS: Six healthy and 14 PLN dogs.

methodsPlatelet aggregometry using adenosine diphosphate (ADP), arachidonic acid (AA), and saline was performed in healthy dogs at baseline and 1-week postclopidogrel administration to identify responders or nonresponders. A decrease of ≥60% for ADP or ≥30% for AA at 1 or 3 hours postpill was used to define a responder. At 1 and 3 hours postclopidogrel, [CM] and PA were measured in healthy and PLN dogs. Platelet aggregometry was performed in PLN dogs at baseline, 1, 6, and 12 weeks after clopidogrel or aspirin administration.

resultsIn PLN dogs receiving clopidogrel, PA differed from baseline at all time points for ADP but not for AA at any time point. Most dogs responded at 1 or both time points except for 1 dog that showed no response. For PLN dogs receiving aspirin, no differences from baseline were observed at any time point for either ADP or AA. No differences in [CM] were found at either time point between healthy and PLN dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Platelet aggregometry may represent an objective method to evaluate response to clopidogrel or aspirin treatment and PLN dogs appear to metabolize clopidogrel similarly to healthy dogs.