Misleading tacrolimus concentration value in blood taken from a catheter used for tacrolimus administration.
OBJECTIVE
A misleading blood tacrolimus concentration (BTC) value caused by the contamination of a central venous catheter previously used for tacrolimus administration is described.


CONCLUSIONS
A 59-year-old woman with severe chronic obstructive pulmonary disease successfully underwent double lung transplantation. In the intensive care unit, she received a continuous i.v. infusion of tacrolimus from days 1 to 5 after transplantation through the distal lumen of a polyurethane triple-lumen central venous catheter. The catheter lumen was flushed twice a day with 0.9% sodium chloride injection. The proximal lumen was used for blood sampling after being flushed; the first 10 mL of blood was discarded. BTCs determined in whole blood one, four, and five days after transplantation were within the therapeutic range of 5-15 ng/mL. On day five the patient was transferred to the thoracic surgery ward and was switched to oral tacrolimus 1.5 mg twice daily. The BTC on day 6 was unexpectedly high at 134.5 ng/mL. The patient's clinical status was normal, and no signs of tacrolimus toxicity were observed. On day 7, blood samples were drawn from a peripheral vein and simultaneously through the central venous catheter. Although the central venous catheter had not been exposed to tacrolimus during the preceding two days, it yielded blood with a BTC eight times higher than the BTC in blood from the peripheral vein (41.4 ng/mL versus 5.1 ng/mL).


CONCLUSIONS
The collection of blood from a central venous catheter lumen that had been used for tacrolimus administration resulted in a BTC about eight times higher than what was measured in peripheral blood.
Grouzmann
Eric
E
Division of Clinical Pharmacology and Toxicology, Lausanne University Medical School, Lausanne, Switzerland. eric.grouzmann@chuv.ch
Buclin
Thierry
T
Biollaz
Jérôme
J
D002405:Catheterization, Central Venous; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D016040:Lung Transplantation; D008875:Middle Aged; D016559:Tacrolimus / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics
D007166:Immunosuppressive Agents; D016559:Tacrolimus