Duration of etidronate effect demonstrated by serial bone scintigraphy.

There have been several reports of etidronate disodium (EHDP) interference upon the biodistribution of 99mTc-methylene diphosphonate (MDP). With the increasing use of etidronate for the treatment of Paget's disease, hypercalcemia, and osteoporosis, nuclear physicians can expect to encounter increasing numbers of cases in which EHDP-induced artifacts impair the diagnostic utility of bone scans. The temporal duration of this effect is unknown yet obviously important. We report serial bone scintigraphy in a patient who received a single dose of EHDP for hypercalcemia. Normal biodistribution of 99mTc-MDP was noted at 15 days, suggesting that 2 wk are sufficient before performing a bone scan after a single intravenous dose of etidronate.