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Formulation and Delivery - Biomolecular

(M1230-06-35) Development of a 4-Day Lidocaine Microreservoir Transdermal Delivery System

Monday, November 10, 2025
12:30 PM - 1:30 PM CT
Purpose: The objective of the study was to develop and characterize a lidocaine transdermal patch using micro-reservoir systems of drug-loaded polymer that have a very large surface area, resulting in concentrated micro-reservoirs of the drug within the polymer (DOT Matrix technology). These micro-reservoirs can hold a substantial amount of the drug. When drug solubilized in acrylate pressure-sensitive adhesive (PSA) is added to the silicon PSA, concentrated drug micro-reservoirs are formed. This results in a high concentration gradient of the drug when the blend is cast to form a patch, which facilitates effective diffusion across the skin(1). Postherpetic neuralgia (PHN) is a chronic neuropathic pain syndrome that arises as the most common complication of shingles, or herpes zoster, following the reactivation of the varicella zoster virus in individuals who have previously had chickenpox. Characterized by persistent pain in the area where the shingles rash once appeared, PHN is defined as pain lasting at least three months after the resolution of the acute herpes zoster rash(2). Lidocaine is an amide-type local anesthetic agent that acts by stabilizing neuronal membranes. It is an FDA-approved medication for the treatment of PHN. In this study, lidocaine was chosen as the model drug due to its favorable physicochemical properties, specifically a molecular weight of 234.343 g/mol and a log P of 2.843, making it ideal for transdermal delivery to evaluate whether dot-matrix patch enhances drug delivery compared to conventional drug-in-adhesive patches.

Methods: A dual-polymer system comprising an acrylic polymer and a silicone polymer was prepared. Initially, a highly concentrated solution of the drug is solubilized within the acrylic polymer matrix. Subsequently, this drug-polymer solution is blended with the silicone polymer to form the final adhesive formulation and is cast to form a patch. The solvent casting method was used to prepare the lidocaine matrix-type patches (Table 1). Four patch formulations (P1, P2, P3, and P4) were developed using various pressure sensitive adhesives (PSAs)—specifically, acrylate-based (Duro-Tak 87-2287), silicone-based (BIO-PSA 7-4302), and hybrid combinations of both adhesive types and evaluated with 1xPBS as the receptor solution (n=4). These formulations underwent evaluation for their ability to facilitate lidocaine permeation through dermatomed porcine ear skin. To ensure optimal patch performance, multiple formulation parameters were systematically optimized, including drying duration, release liner, backing membrane, and drug concentration. The transdermal delivery efficiency was assessed through standardized in vitro permeation testing and in vitro release testing protocols. Quantitative analysis of the delivered lidocaine was conducted using a validated high-performance liquid chromatography (HPLC) method. Statistical evaluation of differences between the formulation groups was performed using one-way analysis of variance (ANOVA), with statistical significance established at p< 0.05.

Results: The drug loading in each adhesive was determined by saturation solubility and slide crystallization studies. The average cumulative amount of drug permeated through dermatomed porcine skin after 4 days was calculated to be 1354.99 ± 176.35, 221.20 ± 34.26, 572.51 ± 76.17 and 578.66 ± 38.46 (µg/cm2) for P1, P2, P3 and P4 respectively. While P1, P3 and P4 were able to reach the therapeutic target for four days, P2 didn’t meet the target dose. The permeation profile of lidocaine is shown in Figure 1a and Cumulative amount of lidocaine delivered by all the different TDS in 96 hours and their comparison is shown in Figure 1c. IVRT studies were carried out using a dialysis membrane, to observe the drug release patterns from the lidocaine TDS. The average cumulative drug release percentages after 4 days were calculated to be 100% in 24 h for P1 whereas the P2, P3 and P4 released 81.87, 93.37, 82.36 % respectively, suggesting micro-reservoir systems gives more sustained release of drug when compared to burst release in acrylate patch(P1). The release profile of lidocaine TDS is shown in Figure 1b.

Conclusion: Among the TDS P1, P3 and P4 significantly enhanced lidocaine permeation across dermatomed porcine ear skin, with P1 achieving the highest delivery of 1354.99 ± 176.35 µg/cm² over four days. Though P1 delivering the highest, the micro-reservoir system patches (P3 and P4) were able to meet the target for four days with less drug loading compared to P1. DOT matrix technology enables extended delivery duration thereby enhancing patient compatibility. From the release studies we can conclude that this approach allows for sustained drug release, maintaining therapeutic drug levels over an extended period while reducing the total amount of drug required and associated side effects.

References: 1. Wiedersberg S, Guy RH. Transdermal drug delivery: 30+ years of war and still fighting! Journal of controlled Release. 2014;190:150–6.
2. Hadley GR, Gayle JA, Ripoll J, Jones MR, Argoff CE, Kaye RJ, et al. Post-herpetic Neuralgia: a Review. Curr Pain Headache Rep. 2016 Feb 15;20(3):17.


Table 1: Composition of Transdermal delivery system (TDS)


Figure 1: a) Permeation profile of Lidocaine across dermatomed porcine skin b) Release profiles for Lidocaine TDS over a 4-day duration across dialysis membrane c) Cumulative amount of Lidocaine delivered by all the different formulations in 96 hours and their comparison