Intravenous pamidronic acid in hypercalcemia due to parathyroid carcinoma.

Three patients aged between 31 and 59 were treated with pamidronic acid (APD) due to severe hypercalcemia caused by parathyroid carcinoma. APD was given in 250 cm3 intravenous saline over a 2 h period in a dose of 0.45 to 0.50 mg/kg per day. Two patients received 6 and the other 9 infusions. Mean serum calcium diminished from 15.7 +/- 1.3 mg/dl to 11.7 +/- 0.6 mg/dl (p less than 0.05). Mean serum ionized calcium decreased from 8.1 mg/dl to 5.5 mg/dl, urinary calcium excretion from 478 mg/24 h to 229 mg/24 h and hydroxyproline from 204 mg/24 h to 117 mg/24 h. Serum calcium returned to pretreatment levels after 5 and 15 days post intravenous APD in two patients. In the third patient treated with 900 mg/day of oral APD, after the intravenous therapy the relapse occurred during the fourth month. The three patients received a second course of intravenous (iv) APD. The effect upon serum calcium (14.6 +/- 1.1 mg/dl to 11.8 +/- 0.6 mg/dl, p less than 0.05) was similar to the one obtained with the first course. Intravenous APD administration appears to be an effective and safe treatment of the severe hypercalcemia due to parathyroid carcinoma. To sustain levels of serum calcium attained in patients with non resectable tumors, a suitable program of iv APD pulses should be established.