Amine Salt Transdermal Patch With In Situ Free-Base Conversion
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Solution Overview
Problem
Transdermal formulations of amine drugs face challenges such as low solubility, recrystallization, volatility, and unstable drug flux due to the use of free base form, which is less stable and less skin-permeable than the salt form.
Innovation Solution
A composition comprising an amine salt form of an active agent and an amphoteric inorganic base compound with a lower pKa than the amine salt, such as sodium bicarbonate, to facilitate in situ conversion to a more skin-permeable free base form, stabilized by solubilizers and plasticizers, and delivered through a transdermal patch with rate-controlling membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the free base form of amine drug is used in transdermal formulation, then skin permeability is improved, but solubility in polymer matrix deteriorates leading to recrystallization
Solution Approach 1:
The patent segments the drug delivery system into two distinct components: the salt form of the amine drug (which provides stability and solubility) and a basic inorganic salt (which provides alkalinity for in-situ conversion). This segmentation allows each component to fulfill its specific function without compromising the other, resolving the contradiction between permeability and solubility stability.
Solution Approach 2:
The patent incorporates a basic inorganic salt (such as magnesium hydroxide, calcium hydroxide, or sodium hydroxide) into the transdermal formulation beforehand. This preliminary action ensures that when the salt form of the amine drug is applied to the skin, the basic environment is already present to facilitate in-situ conversion to the free base form, enabling skin permeability without requiring the drug to be pre-formulated as a volatile free base.
2Speed
If the free base form of amine drug is used in transdermal formulation, then skin permeability is improved, but drug stability deteriorates
Solution Approach 1:
The patent uses a basic inorganic salt as an intermediary substance that mediates the conversion between the stable salt form and the permeable free base form. The basic inorganic salt creates a localized alkaline environment at the application site, allowing the salt form to convert to free base for skin penetration, while the bulk drug remains in the stable salt form within the formulation, thus resolving the contradiction between permeability and stability.
3Stability of the object's composition
If the salt form of amine drug is used in transdermal formulation, then drug stability is improved, but skin permeability deteriorates
Solution Approach 1:
The patent exploits parameter changes in the local environment (pH) to transform the drug's properties. By incorporating basic inorganic salts, the formulation creates a localized increase in pH at the skin interface, which triggers the conversion of the salt form to the free base form. This parameter change enables the drug to exhibit high skin permeability only where needed, while maintaining stability in the formulation reservoir.
4Speed
If the free base form of amine drug is used in transdermal formulation, then skin permeability is improved, but drug flux control deteriorates
Solution Approach 1:
The patent introduces a dynamic conversion mechanism where the drug exists in equilibrium between salt form and free base form through the action of basic inorganic salts. This dynamic system allows the formulation to self-regulate drug flux: as free base is consumed by skin permeation, more salt converts to free base, maintaining a relatively constant delivery rate over time, thus improving flux control while preserving high permeability.
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 composition maintains solubility and stability of the amine drug, allowing for consistent and prolonged transdermal delivery of therapeutically effective concentrations over several days.
Implementation Method 1
Sodium bicarbonate in situ conversion driven transdermal delivery of amine drug
Data Source
AI summary
Compositions, devices, and methods for transdermal administration of active agents provided in their salt form instead of neutral form are provided.