Influence of different indwelling lines on the measurement of blood cyclosporin A levels.

We studied in vivo and in vitro the possible influence of the indwelling line on the measurement of cyclosporin A (CSA) levels. CSA levels measured in samples taken from the catheter lumen used for CSA administration were significantly higher than those taken either from a second lumen or from a peripheral vein. Reversible fixation of the drug to the catheter walls might explain this alteration. The degree of fixation varies for different types of plastic material.