Rivastigmine Transdermal Patch Polymer Matrix Stability
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Solution Overview
Problem
Rivastigmine, used in transdermal patches for treating Alzheimer's and Parkinson's dementia, tends to degrade due to the presence of oxygen, even with a closed polymer matrix and antioxidants, highlighting the need for enhanced stability without additional antioxidants.
Innovation Solution
A transdermal therapeutic system (TTS) with a polymer matrix in the reservoir layer that contains neither hydroxyl groups nor carboxyl groups, utilizing polyacrylates and polyisobutylene polymers to maintain the stability of rivastigmine, ensuring minimal degradation over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If antioxidants are added to the reservoir layer, then the stability of rivastigmine is improved, but the complexity of the formulation increases and potential side effects increase
Solution Approach 1:
The patent removes antioxidants from the formulation entirely, extracting the problematic component that caused degradation while seeking alternative solutions through polymer selection and reservoir design to maintain stability without additives
Solution Approach 2:
The patent changes the chemical parameters of the polymer matrix by selecting polymers with specific functional groups (or lack thereof) that create a more stable environment for rivastigmine, thereby improving stability through material selection rather than additives
2Ease of operation
If polymers with hydroxyl or carboxyl groups are used in the reservoir layer, then adhesive properties and skin compatibility are improved, but rivastigmine degradation is accelerated
Solution Approach 1:
The patent applies different properties to different layers: the reservoir layer uses polymers without hydroxyl or carboxyl groups to ensure stability, while adhesive properties are achieved through the adhesive layer or surface treatment of the reservoir, allowing each layer to optimize its specific function
Solution Approach 2:
The patent uses composite polymer systems in the reservoir layer that combine materials with complementary properties, selecting polymers that provide both the necessary mechanical properties and chemical stability without containing degrading functional groups
3Stability of the object's composition
If a closed polymer matrix is used to prevent oxygen contact, then rivastigmine stability is improved, but oxygen penetration still occurs leading to degradation
Solution Approach 1:
The patent creates an inert chemical environment within the reservoir by selecting polymers that do not contain reactive functional groups (hydroxyl or carboxyl groups) that could facilitate oxidation, thereby chemically preventing degradation rather than just physically blocking oxygen
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 TTS demonstrates adequate stability with less than 1% contamination after one month at 40°C and 75% relative humidity, and less than 0.5% after three months, without the need for antioxidants, maintaining the active substance's integrity.
Implementation Method 1
Rivastigmine, used in transdermal patches for treating Alzheimer's and Parkinson's dementia, tends to degrade due to the presence of oxygen
Implementation Method 2
The reservoir is typically constituted of the active substance in a pharmaceutically acceptable, pressure-sensitive adhesive and is in contact with the surface of the skin, whereby the active substance is released into the body of the patient by means of transdermal diffusion
Data Source
AI summary
The present invention relates to a transdermal therapeutic system for administering an active substance through the skin, comprising:a) a cover layer,b) a reservoir present on the cover layer, comprising a polymer matrix comprising the active substance,c) an adhesive layer present on the reservoir comprising a contact adhesive, andd) a removable layer present on the adhesive layer,the active substance being rivastigmine, a physiologically compatible salt, hydrate, solvate or derivative thereof,characterized in that the polymer matrix of the reservoir comprises neither hydroxyl groups nor carboxyl groups.