Lidocaine Hydrogel Patch Crystallization Control
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Solution Overview
Problem
Conventional lidocaine-containing hydrogel patches experience crystallization and precipitation of lidocaine over time, which reduces skin permeability and effectiveness.
Innovation Solution
A lidocaine-containing hydrogel patch with a support layer and an adhesive layer containing 3-8% lidocaine or its pharmaceutically acceptable salts, 0.3-1% oleic acid, and a pH of 6.8-7.4, along with acid-treated gelatin, to enhance skin permeability and prevent crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lidocaine is contained in the gel base of conventional hydrogel patches, then the patch can provide local anesthetic effect, but lidocaine crystallizes and precipitates over time
Solution Approach 1:
The patent changes the pH parameter of the adhesive layer to a specific range (6.8-7.4) and controls the lidocaine content (3-8% by mass) to prevent crystallization while maintaining anesthetic effect. This parameter optimization resolves the contradiction between reliability and stability.
Solution Approach 2:
The patent creates a composite adhesive layer system combining lidocaine, oleic acid, and pH-adjusting agents. This composite formulation prevents lidocaine crystallization through synergistic interactions, maintaining both therapeutic effect and compositional stability over time.
2Stability of the object's composition
If the pH of the adhesive layer is adjusted to suppress lidocaine precipitation, then crystallization is reduced, but skin permeability may be compromised
Solution Approach 1:
The patent optimizes the pH parameter to a specific range (6.8-7.4) that simultaneously achieves both precipitation suppression and adequate skin permeability. This precise parameter control resolves the contradiction between stability and speed.
Solution Approach 2:
The patent introduces oleic acid as an intermediary substance that facilitates lidocaine permeation through the skin while the pH-adjusted environment prevents crystallization. The oleic acid acts as a mediator that maintains both stability and permeability.
3Speed
If oleic acid is added as a percutaneous absorption accelerator, then skin permeability of lidocaine is improved, but the formulation complexity increases
Solution Approach 1:
The patent makes oleic acid serve multiple functions: it acts as both a percutaneous absorption accelerator to improve skin permeability and as a stabilizing agent in the adhesive layer formulation. This multi-functionality reduces overall formulation complexity despite adding oleic acid.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly improves skin permeability of lidocaine while effectively suppressing its crystallization, maintaining patch effectiveness and adhesiveness over time.
Implementation Method 1
oleic acid, which is ordinarily used as a percutaneous absorption accelerator
Implementation Method 2
the precipitation of lidocaine can be sufficiently suppressed by causing a specific amount of oleic acid to be contained in the adhesive layer, and by adjusting the pH of the adhesive layer
Data Source
Figure 1
AI summary
A lidocaine-containing hydrogel patch comprising: a support layer; and a adhesive layer stacked on a surface of the support layer, wherein the adhesive layer comprises at least one selected from the group consisting of lidocaine and pharmaceutically acceptable salts thereof, a total content of the lidocaine and the pharmaceutically acceptable salts thereof is 3 to 8% by mass relative to an entire mass of the adhesive layer, the adhesive layer further comprises oleic acid in an amount of 0.3 to 1% by mass relative to the entire mass of the adhesive layer, and a pH of the adhesive layer is 6.8 to 7.4.