Carmoterol Nebulizer Formulation pH Stabilization
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Solution Overview
Problem
Carmoterol, a long-acting beta 2-agonist, faces challenges with chemical stability in aqueous solutions due to oxidation and degradation, particularly at low concentrations, which is exacerbated by molecular oxygen and heavy metal ions, necessitating a stable propellant-free formulation for effective administration in respiratory diseases like asthma and COPD.
Innovation Solution
A liquid, propellant-free pharmaceutical formulation with a water-soluble salt of carmoterol, utilizing an aqueous solution with at least 50% water, a co-solvent, and citric acid as a buffering agent to maintain a pH between 4.0 and 5.0, enhancing chemical stability and shelf-life for nebulization administration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carmoterol is formulated at low concentration to achieve high potency, then therapeutic effectiveness is improved, but chemical stability deteriorates due to oxidation and degradation
Solution Approach 1:
The patent applies parameter changes by optimizing the pH to a specific range (4.0-5.0) and using citric acid as a buffering agent to maintain this pH. This chemical parameter adjustment stabilizes carmoterol at low concentrations by preventing oxidation and degradation, thus resolving the contradiction between low concentration formulation and chemical stability
Solution Approach 2:
The patent introduces citric acid as an intermediary substance that acts as a buffering agent and stabilizer. This intermediary maintains the pH within the optimal range and protects carmoterol from oxidation by heavy metal ions and molecular oxygen, enabling stable formulation at low concentrations
2Ease of operation
If aqueous formulation is used for easy administration by nebulisation, then ease of operation is improved, but chemical stability deteriorates due to oxidation by molecular oxygen and heavy metal ions
Solution Approach 1:
Citric acid serves as an intermediary that chelates heavy metal ions and maintains pH, protecting carmoterol from oxidation while allowing the formulation to remain aqueous and suitable for nebulisation administration
Solution Approach 2:
The patent creates a chemically inert environment by using citric acid to buffer the solution and prevent oxidation reactions, effectively protecting the drug from reacting with molecular oxygen and heavy metal ions present in the aqueous formulation
3Device complexity
If propellant-free formulation is used to simplify administration, then device complexity is reduced, but shelf-life and stability deteriorate
Solution Approach 1:
By changing the pH parameter to 4.0-5.0 and using citric acid as a stabilizer, the patent achieves chemical stability of carmoterol in a simple propellant-free aqueous formulation, thereby extending shelf-life without increasing device complexity
Solution Approach 2:
The patent employs a simple, disposable nebuliser formulation that is chemically stabilized through pH control and citric acid addition, allowing the use of a straightforward propellant-free system with adequate shelf-life for commercial distribution
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 formulation ensures substantial chemical stability of carmoterol over time, maintaining less than 5% assay change after six months under accelerated conditions, suitable for commercial distribution and use, with improved stability compared to other buffering agents and pH ranges.
Implementation Method 1
citric acid as a buffering agent to maintain a pH between 4.0 and 5.0
Implementation Method 2
carmoterol undergoes oxidation of the hydroxyl group present on the alkylamino side chain of the molecule
Data Source
Figure 1
AI summary
The invention relates to a liquid, propellant-free pharmaceutical formulation in the form of ready-to-use preparation for administration by nebulisatioη comprising a water soluble salt of the beta2-agonist 8-hydroxy-5- [1-hydroxy-2-[[2-(4-methoxyphenyl)-1-methylethyl]amino]ethyl]-2( 1H)- quinolinone as active ingredient. The active ingredient is chemically stable in the formulation, and said formulation is provided of an adequate shelf-life suitable for commercial distribution, storage and use.