SURFACE-MODIFIED NIOSOME GEL FOR ENHANCED TRANSDERMAL DELIVERY OF DULOXETINE IN NEUROPATHIC PAIN: A COMPREHENSIVE REVIEW

Neuropathic pain is a chronic disorder caused by injury or disease affecting the somatosensory nervous system and is commonly associated with diabetic peripheral neuropathy, postherpetic neuralgia, spinal cord injury, multiple sclerosis, and chemotherapy-induced peripheral neuropathy. Duloxetine hydrochloride, a selective serotonin–norepinephrine reuptake inhibitor (SNRI), is a first-line drug for neuropathic pain management. However, its oral administration is limited by extensive first-pass metabolism, gastrointestinal adverse effects, variable bioavailability, and reduced patient compliance during long-term therapy. Transdermal drug delivery systems (TDDS) have emerged as a promising alternative by bypassing first-pass metabolism, providing sustained drug release, maintaining stable plasma drug concentrations, and improving patient compliance. Among various nanocarrier systems, niosomes have gained considerable attention because of their ability to encapsulate both hydrophilic and lipophilic drugs, enhance skin permeation, improve drug stability, and provide controlled drug release. Furthermore, surface modification of niosomes with chitosan enhances vesicle stability, bioadhesion, skin permeation, and prolonged drug retention, thereby improving therapeutic performance. This review discusses the pathophysiology of neuropathic pain, pharmacological profile of duloxetine, principles of transdermal drug delivery, niosomal drug delivery systems, and the role of chitosan in surface modification. It also summarizes formulation methods, physicochemical characterization, in vitro and ex vivo evaluation, and formulation optimization using Quality by Design (QbD) and Box–Behnken Design. Overall, surface-modified niosomal gel represents a promising strategy for enhancing the transdermal delivery, therapeutic efficacy, and safety of duloxetine in the management of neuropathic pain.