Treatment of ionized hypercalcemia in 12 cats (2006-2008) using PO-administered alendronate

Background: Long-term treatment of cats with ionized hypercalcemia using alendronate has not been evaluated.

Hypothesis/objectives: Alendronate is well tolerated in treatment of ionized hypercalcemia in cats.

Animals: A total of 12 cats with ionized hypercalcemia.

Methods: Prospective study of 12 cats with ionized hypercalcemia of idiopathic origin was identified by telephone and email communication with a convenience sample of consulting veterinarians. Cats were treated with alendronate at a dose of 5-20 mg per feline PO q7d. Serum ionized calcium concentration (iCa) was measured before beginning treatment with alendronate, and after 1, 3, and 6 months of treatment. Alendronate dosage was adjusted according to iCa. Evaluation included physical examination, CBC, biochemistry profile, and diagnostic imaging. The owners and referring veterinarians were questioned about any observed adverse effects. The Wilcoxon matched-pairs signed rank test was used to compare baseline iCa to iCa at different time periods.

Results: Alendronate treatment resulted in a decrease in iCa in all 12 cats. The median percentage change in iCa was -13.2%, -15.9%, and -18.1% (range, -29.6 to +7.6; -30.5 to -1.9; -45.8 to +1.5%) at the 1, 3, and 6 month time points, respectively. Baseline iCa was significantly different from 1 month (P = .0042), 3 months (P = .0005), and 6 months (P = .0015). No adverse effects were reported for any of the cats.

Conclusions and clinical importance: Alendronate was well tolerated and decreased iCa in most cats for the 6-month period of observation.