Short-Term Omeprazole Use Does Not Affect Serum Calcium Concentrations and Bone Density in Horses

Omeprazole is used to treat gastric ulcers in horses. In some human and experimental animal studies, proton pump inhibitor use has been associated with a change in bone density or fracture risk. This study evaluated the effects of administration of omeprazole for 60 days and its effects on serum total calcium, ionized serum calcium, bone mineral content (BMC), and bone mineral density (BMD) in horses. Blood samples and bone biopsies from the tibia were collected from 10 geldings aged 2 and 3 years old before beginning treatment. Horses were administered either 4 mg/kg omeprazole paste or an equal volume of vehicle only paste orally once per day for 60 days. Blood samples were taken at days 7, 14, 21, 28, 35, 42, 49, 56, and 60. Serum total calcium and ionized calcium were measured on all samples. Horses were euthanized on day 60, and bone was harvested from all horses from the contralateral tibia. In addition, the third metacarpal bones and proximal femurs were harvested from each subject. Bone samples were evaluated for BMD and BMC using peripheral quantitative computed tomography (pQCT). Serum total calcium and ionized calcium concentrations were not significantly different between treated and control groups. Bone density and composition were also not significantly different when compared between control and treatment groups. Short-term administration of omeprazole does not significantly affect serum total calcium and ionized serum calcium concentrations nor does it affect bone density or BMC in normal horses as measured with pQCT.