Guanfacine Hydrochloride Stability via pH Control
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Solution Overview
Problem
Existing guanfacine hydrochloride preparations do not effectively suppress the increase of related substances due to hydrolysis over time, which affects stability and pharmacokinetic profiles.
Innovation Solution
Incorporating stability-improving additives such as potassium dihydrogen phosphate, phosphoric acid, carmellose, microcrystalline cellulose, carmellose calcium, low-substituted hydroxypropylcellulose, and hypromellose phthalate into the guanfacine hydrochloride preparation, with concentrations ranging from 0.5% to 25% by weight, to suppress the increase of related substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guanfacine hydrochloride is formulated as a pharmaceutical preparation, then therapeutic efficacy for ADHD is achieved, but hydrolysis increases related substances over time
Solution Approach 1:
The patent introduces pH-adjusting agents (acids such as hydrochloric acid, phosphoric acid, citric acid, or bases such as sodium hydroxide, potassium hydroxide) as intermediary substances to control the microenvironment pH around guanfacine hydrochloride. This mediator approach maintains pH within 2-6 range, preventing hydrolysis without directly modifying the active ingredient itself.
Solution Approach 2:
The patent applies parameter changes by controlling the pH parameter of the pharmaceutical preparation to within the range of 2-6. This parameter control prevents the drug from existing in a pH range that would promote hydrolysis, thereby suppressing the formation of related substances while maintaining therapeutic efficacy.
2Quantity of substance
If pH-dependent dissolution is utilized for guanfacine hydrochloride, then solubility is improved at lower pH, but pH-dependency creates stability issues
Solution Approach 1:
The patent applies local quality by creating a localized acidic or basic microenvironment around the guanfacine hydrochloride particles using pH-adjusting agents. This local pH control (maintained between 2-6) ensures high solubility at the drug site while preventing systemic pH-dependency issues and hydrolysis throughout the preparation.
Solution Approach 2:
The patent changes the pH parameter to within the optimal range of 2-6, transforming the dissolution behavior from highly pH-dependent to controlled pH-dependent dissolution. This parameter optimization maintains solubility benefits while eliminating the instability associated with extreme pH values.
3Ease of manufacture
If existing formulations are used without pH control, then manufacturing simplicity is maintained, but hydrolysis-related stability problems occur
Solution Approach 1:
The patent employs self-service by selecting pH-adjusting agents from common pharmaceutical excipients that are already part of standard formulation practices. These agents (acids like hydrochloric acid or bases like sodium hydroxide) automatically maintain pH within the stable range, providing self-regulating pH control without complex additional mechanisms.
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 use of these additives significantly reduces the hydrolysis-related increase in related substances, enhancing the stability and therapeutic efficacy of the guanfacine hydrochloride preparation.
Implementation Method 1
the increase of related substances with time due to hydrolysis is suppressed
Data Source
AI summary
An object of the present invention is to provide a guanfacine hydrochloride preparation in which an increase of related substances with time due to hydrolysis is suppressed. According to an embodiment of the present invention, a guanfacine hydrochloride preparation is provided containing one or more stability-improving additives selected from a group consisting of potassium dihydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate anhydrous, carmellose, microcrystalline cellulose, carmellose calcium, low-substituted hydroxypropylcellulose, and hypromellose phthalate.