Systemic and Local FK506 (Tacrolimus) and its Application in Peripheral Nerve Surgery

Peripheral nerve injuries (PNI) are common and frequently afflict otherwise healthy individuals after traumatic or iatrogenic events. Adjuvant therapies to improve functional outcomes after surgical repair of PNI have been investigated extensively in preclinical studies; however, to date, none have been clinically proven to have a notable therapeutic effect. FK506 (tacrolimus), a US Food and Drug Administration–approved systemic immunosuppressant, has demonstrated promising neuro-regenerative properties in both animal studies and clinical reports, but its adverse effects when systemically administered have precluded its broader applicability for patients with PNI. Recent advances in bioengineered drug delivery systems have made local FK506 delivery to a site of PNI an intriguing method of promoting peripheral nerve regeneration, with promising results in preclinical translational investigations. This review summarizes the preclinical and clinical evidence for FK506's beneficial effect in promoting peripheral nerve regeneration when administered systemically and locally.