Buffered Lisdexamfetamine Oral Solution for Aqueous Stability
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Solution Overview
Problem
The development of stable liquid formulations of lisdexamfetamine is hindered by degradation at alkaline and oxidative conditions, and existing stabilizing excipients do not adequately enhance the physicochemical stability of lisdexamfetamine salts in aqueous solutions.
Innovation Solution
A physicochemically stable oral pharmaceutical solution comprising a pharmaceutically acceptable salt of lisdexamfetamine, formulated with a buffer and a cosolvent such as a glycol or polyol, maintaining a pH of 5.5 to 9.0, which enhances stability and prevents hydrolysis and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lisdexamfetamine is formulated as an aqueous solution, then ease of administration and patient compliance are improved, but chemical stability and shelf life deteriorate due to hydrolysis and oxidation
Solution Approach 1:
The patent introduces multiple intermediary substances including antioxidants (ascorbic acid, sodium metabisulfite), chelating agents (disodium edetate), and buffering agents (citric acid, sodium citrate) that mediate between the active ingredient and the aqueous environment. These intermediaries protect lisdexamfetamine from direct contact with degrading factors like oxygen and water, enabling stable aqueous formulation.
Solution Approach 2:
The patent systematically adjusts critical parameters including pH (maintained between 3-7 using citrate buffer), temperature (storage at 4°C or 25°C), oxygen exposure (nitrogen headspace), and concentrations of stabilizing agents. These parameter changes create optimal conditions that prevent degradation while maintaining solution stability.
2Duration of action of stationary object
If stabilizing excipients are added to enhance chemical stability, then shelf life is improved, but formulation complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines multiple stabilizing functions into a unified formulation system where antioxidants, chelating agents, and buffering agents work synergistically. This merging of functions into a single aqueous solution formulation simplifies manufacturing compared to multiple separate dosage forms while achieving comprehensive protection against degradation.
Solution Approach 2:
The patent creates an inert environment within the aqueous formulation by incorporating nitrogen headspace and oxygen-scavenging antioxidants, effectively excluding oxygen without requiring complex packaging modifications. This approach extends shelf life while maintaining formulation simplicity.
3Speed
If pH is adjusted to optimize solubility, then dissolution rate is improved, but chemical stability deteriorates due to increased susceptibility to hydrolysis
Solution Approach 1:
The patent optimizes pH to a specific range (3-7) using citrate buffer, balancing solubility and stability requirements. This parameter optimization ensures adequate dissolution rate while minimizing hydrolysis susceptibility through buffered pH control.
Solution Approach 2:
The citrate buffer system acts as an intermediary that maintains pH within the optimal range, preventing extreme pH conditions that would accelerate hydrolysis while ensuring sufficient solubility and dissolution rate for therapeutic effectiveness.
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 solution provides a stable oral pharmaceutical formulation with less than 1.0% total degradation impurities after four weeks at 40°C and 75% relative humidity, offering improved patient compliance and flexible dosing options.
Implementation Method 1
degradation at alkaline and oxidative conditions... prevents hydrolysis and oxidation
Implementation Method 2
degradation at alkaline and oxidative conditions... prevents hydrolysis and oxidation
Data Source
AI summary
Oral pharmaceutical solution comprising a pharmaceutically acceptable salt of lisdexamfetamine, and a pharmaceutically acceptable aqueous carrier comprising a buffer and a cosolvent selected from the group consisting of a glycol, a polyol, and a mixture thereof, wherein the pH of the solution is from 5.5 to 9.0. The oral pharmaceutical solution presents excellent physicochemical stability, even under alkaline conditions.