EN17 - Efficacy and Tolerability of Generic Cinacalcet in Dogs with Primary Hyperparathyroidism

Abstract: Background: Cinacalcet is approved to treat severe hypercalcemia in humans with primary hyperparathyroidism (PHPT) who are unable to undergo parathyroidectomy. In 2018, generic cinacalcet became available and potentially affordable for veterinary patients. Hypothesis: Cinacalcet will be well-tolerated and effective in the management of hypercalcemia associated with PHPT in dogs. Animals: 14 dogs diagnosed with symptomatic PHPT and ionized calcium values greater than 1.5 mmol/L as measured by the Zoetis iSTAT Alinity. Methods: Cinacalcet was initially dosed at 0.5 mg/kg once daily. Dosages were increased weekly until the iCa fell below 1.45 mmol/L, side-effects developed, or a dose of 10 mg/kg bid was reached. PTH was measured at baseline, and again when the target iCa was achieved. SPSS v24 was used to analyze the data with significance at p < 0.05. Results: Mean iCa concentration was 1.74 ± 0.19 mmol/L at baseline and 1.39 ± 0.28 mmol/L post-cinacalcet (p= 0.033). PTH levels were 13.68 ±7.35 pmol/L pretreatment and 9.96 ± 7.31 pmol/L post-cinacalcet (p = 0.194). With doses ranging from 1 mg/kg every 4 days to 9.4 mg/kg bid, 11 (78%) dogs achieved the target iCa < 1.45 mmol/L. The average number of days dogs remained within target iCa was 33.6 days (7-84). Side-effects were observed in 64% of dogs: lethargy and anorexia (9), vomiting (2), and nonhypocalcemic associated episodes of shaking (3). Conclusion: Cinacalcet was effective in significantly decreasing iCa in dogs with PHPT. However, there was considerable inter-individual variation in dose response, side-effects, and the duration of within-target iCa.