Level of clodronate in bone after single and repeated subcutaneous injections in rats

The levels of clodronate in bone and plasma were determined in rats after subcutaneous injection of a mixture of unlabelled and 14C-labelled disodium clodronate as a single dose (25 mg/5 muCi/kg or of 125 mg/25 muCi/kg), and as repeated doses (25 mg/5 muCi/kg) once or five times a week for five weeks. The level of clodronate in bone increased dose-dependently. However, during repeated administration some saturation in bone was observed. The accumulation of clodronate in femur was higher than in ankle. No clear differences in concentration of clodronate in bone could be seen after different dosage schedules when the total doses were the same.