Acidifying Topcoat for Enteric Coating pH Stability
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Solution Overview
Problem
Existing enteric-coated pharmaceutical dosage forms disintegrate in media with pH up to 5, which is a limitation in ensuring effective and controlled release of active ingredients.
Innovation Solution
A dry powder film coating composition comprising one or more polymers, acidic components, and optional additives like plasticizers and pigments is applied as a topcoat to enteric-coated substrates, enhancing their resistance to disintegration in acidic media by modifying the pH-dependent solubility of the enteric polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an enteric coating is applied to pharmaceutical substrates, then the coating provides pH-dependent release of active ingredients, but the coating disintegrates in media with pH up to 5
Solution Approach 1:
The invention applies a composite coating system consisting of an enteric polymer layer combined with an acidifying topcoat layer. The enteric polymer (such as Eudragit L or S) provides pH-dependent solubility, while the acidifying topcoat (containing polymers like HPMC and acidic components like citric acid or stearic acid) creates a protective barrier that lowers the local pH at the coating-medium interface. This composite structure prevents disintegration in acidic media while maintaining controlled release at higher pH levels.
Solution Approach 2:
The invention changes the chemical parameters of the coating system by incorporating acidic components (citric acid, stearic acid, lactic acid) into the topcoat formulation. These acidic components lower the pH at the coating-medium interface, preventing the enteric polymer from dissolving in acidic media. The parameter change in local pH maintains coating integrity while allowing pH-dependent release when the underlying enteric coating is exposed to higher pH environments.
2Stability of the object's composition
If the enteric coating is made more resistant to acidic media, then disintegration resistance improves, but the pH-dependent release mechanism may be compromised
Solution Approach 1:
The coating system is segmented into distinct functional layers: an inner enteric polymer layer that provides pH-dependent solubility and an outer acidifying topcoat layer that provides acid resistance. This segmentation allows each layer to perform its specific function independently - the topcoat protects against acidic media while the enteric layer maintains pH-responsive release capabilities when exposed to higher pH environments.
Solution Approach 2:
The acidifying topcoat acts as an intermediary layer between the acidic media and the enteric polymer coating. It mediates the interaction by lowering the local pH at the interface, preventing direct contact between acidic media and the enteric polymer, thus preserving the enteric coating's pH-dependent release functionality while providing acid resistance.
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 acidifying topcoat significantly increases the resistance of enteric-coated dosage forms to disintegration in media with pH up to 5, ensuring controlled release and improved stability of active ingredients.
Implementation Method 1
enhancing their resistance to disintegration in acidic media by modifying the pH-dependent solubility of the enteric polymers
Data Source
AI summary
The present invention includes acidifying film coating compositions containing a polymer and an acidic component for use on orally-ingestible substrates such as tablets and the like. The acidifying coating compositions can be applied as an aqueous dispersion to an enteric-coated substrate to increase the disintegration resistance to aqueous media of up to pH 5.0. In preferred aspects, the acidic component is citric acid, lactic acid, stearic acid or mixtures thereof. Methods of preparing the dry film coatings, methods of preparing corresponding aqueous dispersions, methods of applying the coatings to substrates and the coated substrates themselves are also disclosed.