Elevated blood drug levels obtained from indwelling silicon catheters during oral cyclosporine A administration.

Cyclosporine A (CsA) may be bound to and released from the inner surface of central venous catheters resulting in spuriously elevated blood drug levels. We observed this phenomenon in a boy transplanted because of aplastic anemia up to 9 weeks after CsA had been switched from intravenous to oral administration. In comparison to phlebotomy, simultaneous blood sampling from the double lumen catheter resulted in a greater than 10-fold, or two-fold increase in drug levels, respectively, depending on whether or not the line used for prior CsA infusion was selected. Thus, prolonged binding of CsA to the inner surface of venous catheters should also be considered during oral administration.