The effects of
ethane hydroxy diphosphonate (
EHDP) on quantitative bone histology have been studied in 43 pagetic patients treated for 6 months at a dose of 5 mg/kg/day. To determine the
therapeutic effects on pagetic bone and to appreciate the side effects in non-pagetic bone, the patients were biopsied either in pagetic or non-pagetic areas of the ilium before the beginning of the treatment and at 3, 6 and 9 months (i.e. 3 months post-
therapy) after the inception of treatment.
Tetracycline double labelling of bone was performed before biopsies in each patient to measure the calcification rate. The results demonstrate that 5 mg/kg/day
EHDP given for 6 months has a marked antiosteoclastic effect which is prolonged after the
cessation of treatment. Pagetic osteoclasts appear more sensitive to
EHDP than normal osteoclasts. The new bone formed during treatment has a regular lamellar texture. At the same time, the high appositional rate of pagetic bone is reduced to a normal value. Marrow
fibrosis is reduced along with the reduction in the osteoclast population. Thus, pagetic bone changes to bone normal in quantity, quality and metabolism. Dynamically, in nonpagetic areas, a transitory decrease of calcification rate is noted at the end of the treatment, without morphological evidence of
osteomalacia, except for 2 out of 43 cases. Histologically,
EHDP given at a dose of 5 mg/kg/day for 6 months appears to be an effective and safe treatment for
Paget's disease of bone.