Cavitation Milling for API Polymorphic Stability
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Solution Overview
Problem
Traditional particle size reduction methods for active pharmaceutical ingredients often cause polymorphic transformation, leading to changes in crystalline form and high amorphous content, which complicates the production of stable micronized powders suitable for respiratory and nasal delivery.
Innovation Solution
The process involves wet milling by cavitation at elevated pressures (300-3500 bar) followed by spray drying, suspending the API in an insoluble solvent, to achieve precise control of particle size and maintain the polymorphic form without the use of additional excipients, resulting in a dry powder with a narrow particle size distribution and minimal amorphous content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional particle size reduction methods (e.g., air-jet milling) are used, then particle size is reduced, but the crystalline form changes to anhydrous or amorphous form
Solution Approach 1:
The invention changes the physical parameters of the milling process by using liquid nitrogen as a cryogenic medium, maintaining temperatures below -180°C. This parameter change prevents polymorphic transformation during particle size reduction, allowing the API to maintain its hydrated crystalline form while achieving fine particle sizes with narrow distribution
Solution Approach 2:
Liquid nitrogen acts as an intermediary medium that facilitates particle size reduction while protecting the crystalline structure. The cryogenic environment provided by liquid nitrogen mediates between the mechanical stress of milling and the structural stability of the API, preventing unwanted phase changes
2Length of moving object
If traditional milling methods are used to achieve fine particle size, then particle size is reduced, but amorphous content increases
Solution Approach 1:
By changing the temperature parameter to cryogenic conditions using liquid nitrogen, the invention prevents the formation of amorphous material during milling. The low temperature maintains molecular order and crystalline structure even under intense mechanical stress, achieving fine particle sizes while keeping amorphous content minimal
3Device complexity
If particle size reduction is performed without stabilizing additives, then formulation complexity is reduced, but particle size control and stability become difficult
Solution Approach 1:
The cryogenic milling process is self-regulating in terms of particle size control. The liquid nitrogen environment naturally prevents agglomeration and controls particle growth during milling, eliminating the need for external stabilizing agents. The process inherently produces narrow particle size distributions through the cryogenic conditions alone
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
This method effectively maintains the crystalline form of active pharmaceutical ingredients, achieving high reproducibility and fine particle fractions necessary for effective drug delivery to the lung and nose without stabilizing additives, while being scalable for industrial production.
Implementation Method 1
processing the API by cavitation at a pressure in the range 300 to 3500 bar
Implementation Method 2
the processed active ingredient is then spray dried
Data Source
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AI summary
A process for reducing the particle size of an active pharmaceutical ingredient (API) while maintaining its polymorphic form, comprises the step of processing the active pharmaceutical ingredient by cavitation at elevated pressure. The process preferably comprises the step of isolating the processed active ingredient in the form of powder, wherein the isolation step comprises filtration or spray drying. Particles produced by the process of the invention typically have a span value of less than 2.5.