The clearance and bioavailability of pamidronate in patients with breast cancer and bone metastases

The pharmacokinetics and bioavailability of pamidronate were assessed in patients with breast cancer, 6 subjects received the drug intravenously and 7 orally. The initial plasma half-life of pamidronate was short (42 +/- 27 min) and the apparent total plasma clearance was high (471 +/- 298 ml/min). The renal clearance (74 +/- 34 ml/min) was similar to the creatinine clearance (66 +/- 19 ml/min). Most of the renal elimination occurred during and immediately post a 4 h infusion of the drug (23.2 +/- 7.9% in 24 h). The non-renal clearance was ascribed to uptake by bone and deep tissue compartments. Little additional drug appeared in the urine after 24 h. The mean bioavailability was estimated using a parallel study design to be 0.3% for a 300 mg oral dose.