Monthly ibandronate suppresses serum CTX-I within 3 days and maintains a monthly fluctuating pattern of suppression

Bone turnover markers such as serum C-terminal cross-linking telopeptide of type I collagen (CTX-I) can be used to assess drug efficacy in osteoporosis. This study evaluated the pattern of CTX-I suppression in postmenopausal osteoporotic women receiving ibandronate. Ibandronate decreased serum CTX-I levels within 3 days of therapy initiation. Over 6 months, the levels remained suppressed below baseline. This randomized, double-blind, placebo-controlled study evaluated the rapidity of onset and pattern of suppression of the bone resorption marker serum CTX-I in women with postmenopausal osteoporosis (PMO) who received once-monthly oral ibandronate. Women diagnosed with PMO received once-monthly oral ibandronate (150 mg) or placebo for 6 months. Serum CTX-I was measured at baseline and after study dose administration on day 3 (month 1 only) and days 7, 14, 21, and 28 (months 1-6). Bone-specific alkaline phosphatase was measured on days 7 and 28 (months 1-6). This study enrolled 67 women: 49 received ibandronate, 17 received placebo, and one took no study drug. At day 3, median reduction in serum CTX-I from baseline was 70.2% with ibandronate and 6.0% with placebo (difference, -64.2%; 95% confidence interval, -80.3% to -46.2%; p < 0.0001). In women receiving ibandronate, serum CTX-I levels remained consistently below baseline, exhibiting a regular monthly fluctuating pattern of suppression over 6 months. Ibandronate was well-tolerated. Monthly ibandronate decreased serum CTX-I within 3 days. Over 6 months, in women receiving once-monthly ibandronate, serum CTX-I remained suppressed below baseline. A monthly fluctuation, related to time from last dose, was observed.