Tacrolimus

How it works

It binds an intracellular immunophilin to inhibit calcineurin, suppressing T-lymphocyte activation and the production of interleukin-2 and other cytokines.

Prescribing in practice

• Tacrolimus has a narrow therapeutic index and is nephrotoxic, so whole-blood trough concentrations must be monitored and the dose individualised.
• Different oral formulations (immediate-release versus prolonged-release) are not interchangeable, and brand/formulation should be prescribed and dispensed consistently to avoid toxicity or rejection.
• Numerous interactions occur via CYP3A4 and P-glycoprotein, and patients require monitoring for hyperglycaemia, hyperkalaemia, hypertension, neurotoxicity and infection.

Monitoring

Monitor whole-blood tacrolimus trough levels, renal function, electrolytes, blood pressure and blood glucose regularly.

Counselling the patient

• Always take the same brand and formulation, and never switch without specialist advice.
• Avoid grapefruit, attend for blood-level monitoring, and report signs of infection promptly.

Evidence & guidelines

Tacrolimus is a cornerstone of transplant immunosuppression, supported by extensive trial evidence and reinforced by MHRA advice on prescribing by brand.