Development and application of a urine drug concentration method for the evaluation of oral absorption of ibandronate in clinical patients.

Aim: A urine drug concentration method was developed for the evaluation of oral ibandronte absorption based on the fact that ibandronate is excreted unchanged by the kidneys. Methodology: Ibandronate was isolated from the urine matrix by coprecipitated with 2.5 M CaCl2 and 1 M K2HPO4 in basic conditions. After a liquid-liquid extraction, the analytes were derivatized with trimethylsilydiazomethane prior to detection. Results: The calibration curves exhibited excellent linearity (r > 0.99) between 1 and 250 ng/ml in human urine. Ibandronate was recovered >86.5% with the inter- and intraday relative standard deviations less than 15%. Conclusion: The method is selective, accurate, practical and was successfully applied to study the influence of vitamin D3 on the absorption of ibandronate.