TDM Calcineurin Inhibitor Level Interpretation
Drug Level & Context
ng/mL
Steady-state trough (C0)
months
TDM Interpreter
Enter drug level and context for interpretation and dose guidance.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
To interpret tacrolimus and cyclosporine trough levels in solid organ transplant recipients
To guide dose adjustments for calcineurin inhibitors based on therapeutic drug monitoring
To differentiate subtherapeutic, therapeutic, and supratherapeutic drug levels
To tailor immunosuppression targets by organ type and time post-transplant
To identify drug interactions affecting CNI levels
Why TDM Matters
Calcineurin inhibitors (tacrolimus, cyclosporine) have narrow therapeutic indices with significant inter- and intra-patient pharmacokinetic variability. Subtherapeutic levels risk acute rejection; supratherapeutic levels cause nephrotoxicity, neurotoxicity, and metabolic complications. TDM is the standard of care for managing CNI therapy.
How it Works
Tacrolimus (FK506) Targets
| Kidney — Early (0-3 mo) | 8-12 ng/mL |
| Kidney — 3-12 mo | 6-10 ng/mL |
| Kidney — > 12 mo | 4-8 ng/mL |
| Liver — Early (0-3 mo) | 8-12 ng/mL |
| Liver — > 12 mo | 4-8 ng/mL |
| Heart — Early (0-3 mo) | 12-18 ng/mL |
| Heart — Maintenance | 8-12 ng/mL |
| Lung — Early (0-3 mo) | 12-18 ng/mL |
| Lung — Maintenance | 8-12 ng/mL |
| Pancreas — Early | 10-15 ng/mL |
| Pancreas — Maintenance | 6-10 ng/mL |
Cyclosporine (CsA) Targets
| Kidney — Early (0-3 mo) | 200-350 ng/mL |
| Kidney — > 12 mo | 100-200 ng/mL |
| Liver — Early (0-3 mo) | 250-400 ng/mL |
| Liver — > 12 mo | 100-200 ng/mL |
| Heart — Early | 250-400 ng/mL |
| Heart — Maintenance | 150-300 ng/mL |
Clinical Pearls
Drug Interactions Affecting CNI Levels
Azole antifungals (fluconazole, voriconazole, posaconazole) — increase CNI levels significantly
Macrolide antibiotics (erythromycin, clarithromycin) — increase CNI levels
Calcium channel blockers (diltiazem, verapamil) — increase CNI levels
Rifampin — decreases CNI levels substantially (often requires dose doubling)
Anticonvulsants (phenytoin, carbamazepine, phenobarbital) — decrease CNI levels
St John's Wort — decreases CNI levels (contraindicated)
Grapefruit/grapefruit juice — increases CNI levels via CYP3A4 inhibition
Tacrolimus vs. Cyclosporine
Tacrolimus has largely replaced cyclosporine as the CNI of choice in most transplant centres due to superior rejection prophylaxis and graft survival outcomes (particularly in kidney and liver transplantation). Cyclosporine remains in use in selected programs, for specific indications (e.g., heart transplantation with tacrolimus intolerance), and in resource-limited settings where lower cost is a consideration.
Next Steps
Managing Out-of-Range Levels
01
Mildly supratherapeutic (10-25% above target): Reduce dose by 10-20%. Recheck in 3-7 days. Monitor renal function and electrolytes.
02
Significantly supratherapeutic (> 50% above target): Hold next dose. Reduce total daily dose by 25-50%. Recheck in 24-48 hours. Check for drug interactions and renal function.
03
Mildly subtherapeutic (10-25% below target): Increase dose by 10-20%. Assess adherence. Recheck in 5-7 days.
04
Significantly subtherapeutic (< 50% of target): Increase dose by 25-50%. Consider loading dose. Assess for non-adherence, vomiting, diarrhoea, or drug interactions. Recheck in 3-5 days.
The Evidence
KDIGO Transplant Guidelines
KDIGO clinical practice guideline for the care of kidney transplant recipients.
KDIGO Transplant Work Group. • Am J Transplant.. 2009;9(Suppl 3):S1–S155. Comprehensive guideline for transplant care including TDM targets.
AST TDM Guidelines
Therapeutic drug monitoring of immunosuppressant drugs in clinical practice.
Kahan BD et al. • Clin Ther.. 2002;24(3):330–350. Foundational review of CNI TDM principles.
Origins & History
Evolution of CNI TDM
Calcineurin inhibitor TDM has been a cornerstone of transplant medicine since the introduction of cyclosporine in the 1980s and tacrolimus in the 1990s. Target ranges have evolved significantly over time, with modern protocols favouring lower targets than those used in the early post-marketing era — a shift driven by the recognition that nephrotoxicity was being underappreciated at higher levels.
Last Comprehensive Review: 2026-07-17