(R)-Oxybutynin D-Malate Salt Forms for OSA Stability
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Solution Overview
Problem
There is a need for pharmaceutically useful forms of oxybutynin, particularly the R-enantiomer, which is effective for treating conditions associated with pharyngeal airway collapse such as obstructive sleep apnea, and existing forms like racemic oxybutynin hydrochloride may not provide optimal stability and efficacy.
Innovation Solution
Development of novel solid forms of (R)-oxybutynin, including crystalline and amorphous forms of (R)-oxybutynin D-malate and (R)-oxybutynin L-tartrate, characterized by specific XRPD patterns, FT-Raman spectra, and thermal stability, which are prepared using methods involving D-malic acid and L-tartaric acid, respectively, to enhance stability and bioavailability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If racemic oxybutynin hydrochloride is used, then the drug can be administered orally or topically for general smooth muscle relaxation, but it lacks the optimized stability and efficacy required for specific conditions like obstructive sleep apnea
Solution Approach 1:
The racemic mixture is segmented into individual enantiomers through chiral resolution using diastereomeric salt formation. The (R)-enantiomer is isolated and converted to stable solid forms (sulfonate salts and solvates), separating the therapeutically active component from the less effective (S)-enantiomer, thereby improving reliability for specific indications while maintaining adaptability through selective targeting.
Solution Approach 2:
The physical and chemical parameters of oxybutynin are changed by forming stable solid-state structures (sulfonate salts and solvates). These parameter changes enhance stability and bioavailability specifically for the (R)-enantiomer, optimizing its performance for pharyngeal airway collapse treatment while preserving the ability to administer via multiple routes.
2Reliability
If novel solid forms like (R)-oxybutynin D-malate and (R)-oxybutynin L-tartrate are developed, then stability and bioavailability are enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
Chiral resolution is performed in advance during the salt formation step, allowing the (R)-enantiomer to be isolated and converted to stable solid forms before final formulation. This preliminary action simplifies downstream processing by eliminating the need for later chiral separation steps, reducing overall manufacturing complexity while maintaining enhanced stability and bioavailability.
Solution Approach 2:
Chiral acids (D-malic acid, L-tartaric acid) serve as intermediaries in the salt formation process. These intermediaries facilitate chiral resolution and stable solid form generation through diastereomeric salt formation, which can be easily separated and converted back to the free base, thereby enhancing reliability without significantly complicating the manufacturing process.
3Reliability
If the (R)-enantiomer is isolated and converted to stable solid forms, then therapeutic effectiveness for pharyngeal airway collapse is improved, but the production process requires additional chiral resolution steps
Solution Approach 1:
The production process utilizes parameter changes in the form of pH-controlled salt formation and dissolution. By adjusting pH and using chiral acid intermediaries, the (R)-enantiomer is selectively isolated and converted to stable solid forms through well-established pharmaceutical techniques, maintaining ease of manufacture while improving therapeutic effectiveness.
Solution Approach 2:
The less effective (S)-enantiomer is discarded during the chiral resolution process, while the therapeutically valuable (R)-enantiomer is recovered in high purity. This selective recovery approach simplifies the overall process by eliminating the need to handle and formulate the less effective enantiomer, thereby improving therapeutic effectiveness without proportionally increasing manufacturing complexity.
Data Source
AI summary
(R)-Oxybutynin D-malate salts, including crystalline and amorphous forms, are prepared and characterized. Uses of (R)-oxybutynin D-malate for obstructive sleep apnea (OSA) treatment are also disclosed. Solid forms of (R)-oxybutynin L-tartrate are also disclosed.