[Effect of low doses of oral pamidronate (APD) on the calcemia of osteopenic or osteoporotic patients]. / Efecto de bajas dosis del pamidronato (APD) oral sobre la calcemia de pacientes osteopenicas u osteoporoticas.

Oral pamidronate (APD) at high doses (400-900 mg/day) is employed as antiresorptive agent for the treatment of Paget's disease. In some occasions hypocalcemia may occur, and is interpreted as a relative overdosage. To avoid this complication and the consequent PTH release, supplementation with calcium salts is recommended. In osteoporotic syndromes, APD is prescribed at a lower dosage (200 mg/day) and currently calcium or vitamin D are also systematically added. But at this low dose the antiresorptive activity is partial and transient. In order to observe the effects on calcemia of multiple therapy, data from 129 postmenopausal women with the diagnosis of osteopenia or osteoporosis treated with 200 mg/day of APD soft capsules during 6-10 months, were gathered retrospectively. The first group (n: 13) received APD alone; the second group was supplemented with 1 g/day calcium salts (n: 61); the third group received 0.015-0.025 mg/day vitamina D (n: 10); and the fourth received both calcium plus vitamin D (n: 45). In samples of 24 h, urine, calcium, creatinine, hydroxyproline, and serum total calcium were measured before and after therapy. No hypocalcemia was detected. All groups, except the one treated with APD alone, showed a significant trend to increase their calcemia values between normal ranges (Table 1, 2). Only in one patient treated with APD + Ca + vitamin D, hypercalcemia was detected. Measuring HOP/Cr and Ca/Cr in urine as resorption markers, showed that 27% of the APD + Ca group and 33% of the APD + Ca + vitamin D group showed scant or any repercussion on mentioned resorption indexes, meaning that the response to APD could be hindered in those cases. In conclusion, while using low doses of oral APD, calcium salts should not be systematically recommended. There is no trend to hypocalcemia. Furthermore, calcium salts may favor drug interactions and so induce digestive side effects or poor responses. Calcium supplementation should be prescribed only on the basis of low calcium diet and not to prevent APD collateral effects on calcemia.