Tacrolimus

This test measures the amount of tacrolimus in the blood. Tacrolimus is an immunosuppressive drug that is given orally or intravenously to patients who have had a kidney, liver, heart, or other organ transplant. It is a powerful drug that helps to prevent rejection of the transplanted organ by the body. Normally, a person’s immune system would recognise the new organ as foreign and begin to attack it.  Tacrolimus limits this response and helps to prevent organ rejection by reducing the activity of certain immune cells called T-lymphocytes. 

Tacrolimus levels in the blood must be kept within a narrow range. If the concentration is too low organ rejection may occur, if it is too high then the person may have symptoms associated with toxicity. Dosages must be adjusted to an individual. Often people will begin with higher doses of tacrolimus immediately after a transplant and the doses will then be decreased over the next few weeks. Tacrolimus is usually taken twice a day at set intervals before or after meals. When a person takes a dose, blood concentrations rise and peak within about 2 to 3 hours then begin to fall slowly. The blood test is usually measured as a “trough” level. It is timed so that the collection is 12 hours after the dose, and/or prior to the next dose – at the drug’s lowest concentration in the blood.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

Have the blood sample collected 12 hours after the last dose and/or immediately prior to the next dose or as directed by your doctor