Zoledronic acid: 4 mg or 5 mg?

Zoledronic acid is an aminobisphosphonate that is a potent inhibitor of bone resorption.Now there are two kinds of zoledronic acid(4 mg and 5 mg)on the shelf of the pharmacy with different FDA-approved indications(antihypercalcaemia and anti-osteoporosis),which makes clinicians and pharmacists confused.Our hypothesis is that 4 mg zoledronic acid could be effective in osteoporosis patients.Theoretically,the mechanism of the anti-osteoporosis effect and anti-hypercalcaemia effect is to inhibit the osteoclasts,thus reducing the serum Ca2+concentration and improving the bone mineral density.And the anti-osteoporosis effect of zoledronic acid is dose-dependent.What’s more,some clinical trials showed that 4 mg zoledronic acid was effective in treating osteoporosis.Moreover,several clinical trials have demonstrated that zoledronic acid(4 mg)may be effective in countering bone loss resulted from aromatase inhibitor therapy or endocrine therapy.Thus maybe 4-mg dose is enough for both diseases and the 5-mg dose seems unnecessary.We just need to optimize the dosing frequency according to different conditions.