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Purpose <p>Topical delivery of lidocaine is often limited by poor aqueous solubility, restricted skin permeation, and rapid drug release. This study aimed to improve the water solubility of lidocaine and to develop a microemulsion (ME)-based gel capable of providing controlled release and enhanced ex-vivo skin permeation.</p> Methods <p>Lidocaine-loaded microemulsions (MEs) were prepared using castor oil, Tween 80, and propylene glycol through aqueous titration and optimized using a Box–Behnken Design. All prepared MEs were characterized for droplet size (PS), polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE%), and thermodynamic stability. The optimized ME was further examined by transmission electron microscopy (TEM). This optimized ME was then incorporated into a Carbopol gel base to obtain a ME gel suitable for topical application. In-vitro release and ex-vivo permeation studies across excised goat skin were performed for the optimized ME gel and compared with a conventional lidocaine gel. Release kinetics were evaluated using mathematical models. Stability studies were conducted at 25 ± 2&#xa0;°C/60 ± 5% RH and 4 ± 2&#xa0;°C for 60 days.</p> Results <p>The developed MEs exhibited nanosized droplets (&lt; 100&#xa0;nm), low PDI (0.27), ZP ranging from − 31.5 to − 9.43 mV, high EE% (&gt; 90%), and satisfactory thermodynamic stability. TEM confirmed spherical nanoscale droplets. The ME gel demonstrated suitable viscosity and spreadability for topical use. In-vitro release showed sustained diffusion-controlled behavior (85.6 ± 2.7% in 24&#xa0;h) following Higuchi kinetics (R² = 0.971). Ex-vivo permeation from the ME gel was significantly higher than the conventional gel, with approximately two-fold higher steady-state flux (26.57 ± 2.41&#xa0;µg/cm²/h). Stability assessment showed no significant changes in PS, PDI, ZP, EE%, pH, or viscosity over 60 days.</p> Conclusion <p>The lidocaine-loaded ME gel improved drug solubility, provided controlled release, and enhanced ex-vivo permeation while maintaining physicochemical stability. These findings support its potential as a formulation-level strategy for topical lidocaine delivery, pending further in-vivo and pharmacodynamic evaluation.</p>

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Development and Characterization of a Sustained-Release Lidocaine-Loaded Microemulsion Gel for Transdermal Delivery

  • 期刊论文

  • 发表日期：

    2026年2月27日

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  • Umashri A. Kokatanur,
  • Panchaxari M. Dandagi

摘要

Purpose

Topical delivery of lidocaine is often limited by poor aqueous solubility, restricted skin permeation, and rapid drug release. This study aimed to improve the water solubility of lidocaine and to develop a microemulsion (ME)-based gel capable of providing controlled release and enhanced ex-vivo skin permeation.

Methods

Lidocaine-loaded microemulsions (MEs) were prepared using castor oil, Tween 80, and propylene glycol through aqueous titration and optimized using a Box–Behnken Design. All prepared MEs were characterized for droplet size (PS), polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE%), and thermodynamic stability. The optimized ME was further examined by transmission electron microscopy (TEM). This optimized ME was then incorporated into a Carbopol gel base to obtain a ME gel suitable for topical application. In-vitro release and ex-vivo permeation studies across excised goat skin were performed for the optimized ME gel and compared with a conventional lidocaine gel. Release kinetics were evaluated using mathematical models. Stability studies were conducted at 25 ± 2 °C/60 ± 5% RH and 4 ± 2 °C for 60 days.

Results

The developed MEs exhibited nanosized droplets (< 100 nm), low PDI (0.27), ZP ranging from − 31.5 to − 9.43 mV, high EE% (> 90%), and satisfactory thermodynamic stability. TEM confirmed spherical nanoscale droplets. The ME gel demonstrated suitable viscosity and spreadability for topical use. In-vitro release showed sustained diffusion-controlled behavior (85.6 ± 2.7% in 24 h) following Higuchi kinetics (R² = 0.971). Ex-vivo permeation from the ME gel was significantly higher than the conventional gel, with approximately two-fold higher steady-state flux (26.57 ± 2.41 µg/cm²/h). Stability assessment showed no significant changes in PS, PDI, ZP, EE%, pH, or viscosity over 60 days.

Conclusion

The lidocaine-loaded ME gel improved drug solubility, provided controlled release, and enhanced ex-vivo permeation while maintaining physicochemical stability. These findings support its potential as a formulation-level strategy for topical lidocaine delivery, pending further in-vivo and pharmacodynamic evaluation.