Enhanced diclofenac sodium delivery through advanced self-microemulsifying pectin-based transdermal patches

Abstract

Diclofenac sodium (DCFNa) presents significant challenges in local pain relief due to its poor solubility and limited skin permeability. This study aimed to enhance the solubility and skin permeation of DCFNa by developing DCFNa-loaded self-microemulsifying drug delivery system (SMEDDS) embedded pressure-sensitive adhesive (PSA) patch. The solubility of DCFNa in various solvents was evaluated, and a ternary phase diagram was constructed to optimize the SMEDDS formulation. The transdermal patch, composed of pectin and polyacrylate, was optimized using a simplex lattice experimental design to achieve the desired adhesion strength and to select the most suitable patch for skin drug accumulation study. Clove oil, Tween® 80, and propylene glycol were identified as the appropriate oil, surfactant, and co-surfactant, respectively, for achieving highest DCFNa solubility. The SMEDDS was formed with a ratio of 5:35:60 (oil: Smix [1:1 surfactant: co-surfactant]: water), yielding nano-sized droplets (22.64 ± 0.74 nm) and significantly enhancing DCFNa solubility (329.62 ± 10.16 mg/mL) compared to phosphate buffer (5.03 ± 1.01 mg/mL). The DCFNa-loaded SMEDDS demonstrated a 9-fold increase in skin permeability compared to the DCFNa solution. The optimized PSA patch, containing 20 % pectin and 40 % polyacrylate, exhibited superior tacking and peel strength. Additionally, a 1 % DCFNa-loaded SMEDDS patch delivered twice greater drug accumulation in the skin and showed no skin irritation, maintaining better adhesion for up to 24 h compared to commercial patches.