Mechanical properties of bone and skin during recovery after cyclophosphamide administration

The effects of cyclophosphamide were studied 2, 5 and 9 days after terminating a two-week every-second-day intraperitoneal medication in young, male rats. The cytostatic effect was assessed by counting white blood cells (WBC) in arterial blood. WBC counts were reduced by 72% of control values at 2 days and regained normal values at 9 days after an overshooting leucocytosis at 5 days. Compared to control animals, the treated rats had significantly reduced body weights, metaphyseal bending strength and longitudinal growth of the femur at all time intervals observed. The torsional strength of the femur diaphysis and the strength of wounded skin were not affected at 2 days, but significantly reduced at 5 and 9 days. The tensile strength of intact skin was not found to be affected by the drug. From the 5th to the 9th day after ending medication, the curves for control and treated animals were assuming parallel slopes regarding metaphyseal bone strength, longitudinal bone growth and tensile strength of wounds. This may indicate reversion of the drug effects approximately one week after terminating medication.