Tacrolimus (FK506)

Notes

• Tacrolimus is an immunosuppressant drug used in the prophylaxis of organ rejection in patients receiving transplants.
• Tacrolimus is also used in the treatment of some autoimmune diseases.
• Measurement is indicated to establish the correct dose, maintain therapeutic levels and ensure that toxic levels are avoided.

Sample requirements

Samples should be taken just before the next dose (trough level).

For adults, blood taken into a 4mL EDTA tube

For children, blood taken into a 2mL EDTA tube

For infants, blood taken into a 1mL minicollect EDTA tube

Storage/transport

Send at ambient temperature to the laboratory. If unavoidable, samples can be stored refrigerated overnight.

Required information

Relevant clinical details including time of last dose and time of sample (sample should be taken just before the next dose).

Turnaround times

Samples are analysed locally at Gloucestershire Royal Hospital, with a usual turnaround time of 3 working days.

Tacrolimus can be ordered as an urgent test if clinically indicated, but only after discussion with the duty biochemist. Results can be obtained by the end of the working day (Monday – Friday) providing this has been agreed in advance, and appropriately timed samples are received in the laboratory before 12pm.

Reference ranges

The therapeutic range for tacrolimus is 3 - 12 µg/L

Please note:

• As for all immunosuppressive drug measurements, the interpretation of results must be made with regard to factors such as the method used to measure the drug, the time interval between the sample and the last dose, the clinical indication for the use of the drug, the duration of therapy and other drug therapy.
• Individual patients will have a personalised target range that is appropriate for them, as advised by their consultant. Please refer to this when making decisions regarding dose changes, as the target range will vary for each patient according to the type of organ transplant and the post-transplant.

Further information

To learn more about tacrolimus visit Lab Tests Online

North Bristol NHS Trust Information sheet: Drugs interfering with the metabolism of tacrolimus