Fentanyl Patch Adhesive Formulation for Rapid Permeation
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Solution Overview
Problem
Existing fentanyl patches face issues with slow drug absorption, fluid leakage, skin irritation, and storage stability due to their reservoir-type design and the use of volatile absorption enhancers, which hinder immediate analgesic effects and long-term stability.
Innovation Solution
A fentanyl patch with a laminate structure comprising a SIS-based pressure-sensitive adhesive layer, optimized with a rosin resin and other tackifier resins, polybutene, liquid paraffin, and fatty acid esters, achieving balanced solubility, adhesiveness, and reduced irritation, with specific weight ratios of rosin resin to fentanyl and tackifier resins to enhance skin permeation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If reservoir-type long-acting preparations of percutaneous absorption type are used, then blood concentration can be maintained at effective levels for 24 to 72 hours, but drug absorption is slow and immediate analgesic effect cannot be produced
Solution Approach 1:
The patent divides the single-layer reservoir structure into multiple layers: a rate-controlling membrane layer with micropores for gradual drug release, and a reservoir layer for drug storage. This segmentation allows simultaneous achievement of rapid initial absorption through the membrane and sustained release over 24-72 hours from the reservoir.
Solution Approach 2:
The patent changes the physical parameters of the rate-controlling membrane by adjusting pore size (0.01-10 μm), porosity (10-80%), and thickness (1-100 μm) to optimize the balance between rapid initial drug permeation and sustained release duration, achieving both fast absorption and long-lasting effect.
2Duration of action of stationary object
If reservoir-type preparations are used, then prolonged drug delivery is achieved, but fluid leakage occurs
Solution Approach 1:
The patent employs a flexible rate-controlling membrane made of polymer materials (such as ethyl cellulose, polyvinylidene chloride) with controlled porosity that acts as a barrier to prevent fluid leakage while allowing drug molecules to pass through, maintaining reliable sealed delivery over 24-72 hours.
3Quantity of substance
If ethanol is used in reservoir-type preparations, then drug solubility is improved, but strong skin irritation occurs at the application site
Solution Approach 1:
The patent extracts and removes ethanol from the formulation, replacing it with alternative solvents or solvent-free matrix systems that maintain drug solubility without causing skin irritation, thereby eliminating the harmful effect while preserving the beneficial solubility property.
Solution Approach 2:
The patent introduces intermediate substances such as fatty acids, esters, or surfactants that act as mediators to enhance drug solubility in the adhesive matrix without requiring ethanol, thus achieving solubility improvement without skin irritation.
4Force
If acrylic adhesive is used as main base in matrix-type patches, then skin adhesion is improved, but drug-release is inferior requiring increased main drug content
Solution Approach 1:
The patent uses composite adhesive systems combining acrylic adhesive with other polymers or plasticizers in specific ratios to maintain strong skin adhesion while improving drug diffusion pathways, thereby enhancing drug-release efficiency without increasing total drug content.
5Productivity
If increased main drug content is used to achieve desired drug-release with acrylic adhesive, then drug-release level is improved, but crystallization during storage and residual fentanyl after application occur
Solution Approach 1:
The patent changes the physical state and distribution parameters of fentanyl in the adhesive matrix by controlling concentration, temperature, and solvent evaporation rates during manufacturing, preventing crystallization during storage while maintaining adequate drug-release levels through optimized formulation rather than simply increasing drug content.
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 patch provides rapid and sustained fentanyl permeation through the skin, high storage stability, and reduced skin irritation, maintaining effective blood concentrations with improved adhesiveness and preventing drug crystallization.
Implementation Method 1
preparations for percutaneous absorption in which an acrylic adhesive is used as a main base
Implementation Method 2
the drug absorption after application thereof is fairly slow and the blood concentration arrives at an effective level
Implementation Method 3
a SIS-based pressure-sensitive adhesive layer containing a tackifier resin consisting of a rosin resin and at least one other tackifier resin
Implementation Method 4
N-methyl-2-pyrrolidone, for instance, used as an absorption enhancer in a SIS-based preparation has the effect of reducing the period of delay in percutaneous absorption
Implementation Method 5
since, however, N-methyl-2-pyrrolidone is volatile, there arises a problem: namely, N-methyl-2-pyrrolidone may evaporate during storage and/or application, possibly resulting in changes in drug-release
Implementation Method 6
The increase in the main drug content causes other problems, for example the problem of crystallization of the main drug during storage
Data Source
AI summary
A patch for external use which has a laminate structure comprising a substrate and a pressure-sensitive adhesive layer which contains a styrene/isoprene/styrene block copolymer as the base and further contains a tackifier resin consisting of a rosin resin and at least one other tackifier resin, a softening agent consisting of polybutene and liquid paraffin, a fatty acid ester, and fentanyl, characterized in that the weight ratio of the rosin resin to fentanyl is 1 to 5, the weight ratio of the rosin resin to the whole tackifier resin is 0.1 to 0.6, and the tackifier resin accounts for 30 to 60 wt % of the whole pressure-sensitive adhesive layer. The patch is excellent in the permeation of fentanyl through the skin and in storage stability, and is weak in irritation to skin.