How are Calcineurin Inhibitors levels monitored?
CNIs require trough monitoring to ensure an adequate degree of immunosuppression. The trough should be 12 hours after the last dose, so it is imperative the patient take the medication regularly at 12-hour intervals and plan for the lab about 30 minutes prior to the next dose. There is also an extended 24-hour release formulation of tacrolimus. In this case, levels are checked 24 hours after the last dose. Desired drug level varies from center to center, depending on the particular immunosuppression strategy, but the goal in the first year is usually 8 to 12 with lower levels desired targeted further out from transplant
If a drug level is uncharacteristically elevated, when calling the patient, always ask if they had taken the CNI prior to the blood draw to check the level. Another common cause of elevated CNI levels due to increased absorption is diarrhea. If drug levels are either higher or lower than usual, ask if the patient is on any new medications.