Long-term efficacy, safety, and patient acceptability of ibandronate in the treatment of postmenopausal osteoporosis

Several second-generation bisphosphonates (BPs) are approved in osteoporosis treatment. Efficacy and safety depends on potency of farnesyl pyrophosphate synthase (FPPS) inhibition, hydroxyapatite affinity, compliance and adherence. The latter may be influenced by frequency and route of administration. A literature search using "ibandronate", "postmenopausal osteoporosis", "fracture", and "bone mineral density" (BMD) revealed 168 publications. The Phase III BONE study, using low dose 2.5 mg daily oral ibandronate demonstrated 49% relative risk reduction (RRR) in clinical vertebral fracture after 3 years. Non-vertebral fracture (NVF) reduction was demonstrated in a subgroup (pretreatment T-score ≤ -3.0; RRR 69%) and a meta-analysis of high annual doses (150 mg oral monthly or intravenous equivalent of ibandronate; RRR 38%). Hip fracture reduction was not demonstrated. Long-term treatment efficacy has been confirmed over 5 years. Long term safety is comparable to placebo over 3 years apart from flu-like symptoms which are more common with oral monthly and intravenous treatments. No cases of atypical femoral fracture or osteonecrosis of the jaw have been reported in randomized controlled trial studies. Ibandronate inhibits FPPS more than alendronate but less than other BPs which could explain rate of action onset. Ibandronate has a higher affinity for hydroxyapatite compared with risedronate but less than other BPs which could affect skeletal distribution and rate of action offset. High doses (150 mg oral monthly or intravenous equivalent) were superior to low doses (oral 2.5 mg daily) according to 1 year BMD change. Data are limited by patient selection, statistical power, under-dosing, and absence of placebo groups in high dose studies. Ibandronate treatment offers different doses and modalities of administration which could translate into higher adherence rates, an important factor when the two main limitations of BP treatment are initiation and adherence rates. However, lack of consistency in NVF reduction and absence of hip fracture data limits more generalized use of this agent.