Effects of sodium etidronate in combination with low-dose norethindrone in patients administered a long-acting GnRH agonist: a preliminary report.

Objective: To assess the efficacy of combining sodium etidronate with low doses of the 19-nor-testosterone progestin norethindrone or using high doses of norethindrone alone as prophylaxis against the vasomotor instability and bone density loss induced by GnRH agonists alone.
Methods: Eleven patients enrolled in this randomized study received the long-acting GnRH agonist leuprolide acetate 3.75 mg intramuscularly every 4 weeks for 24 weeks. Six patients (group I) self-administered sodium etidronate 400 mg/day orally for 14 days followed by calcium carbonate 500 mg/day orally for the next 42 days during three 56-day cycles. This regimen was supplemented by norethindrone 2.5 mg/day orally. Five patients (group II) self-administered norethindrone 10 mg/day orally. Two sets of controls were used. Group III consisted of ten previously reported patients who received the same GnRH agonist only. Group IV comprised 12 regularly cycling untreated controls. Bone mineral density, vasomotor symptoms, circulating estrogens, and lipids were assessed serially.
Results: The significant vasomotor instability (P < .01) and bone mineral density loss (-4.8 +/- 0.9%; P < .05) experienced by patients in group III was prevented in those in groups I and II despite maintenance of a persistent hypoestrogenic state. Bone density changes in groups I and II were similar to those in untreated controls (group IV). Persistent decreases in high-density lipoprotein (HDL) cholesterol (P = .005) and increases in the low-density lipoprotein-to-HDL ratio (P < .05) were noted only in group II patients receiving supplemental high-dose norethindrone.
Conclusion: These preliminary data suggest that the addition of cyclic sodium etidronate in combination with low-dose norethindrone to GnRH agonists is an effective means of ameliorating the hypoestrogenic side effects induced by GnRH agonist alone.