MTHF Stabilization via Basic pH and Citrate Complex
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Solution Overview
Problem
5,10-methylenetetrahydrofolic acid (MTHF) is highly sensitive to oxidation, leading to instability in aqueous solutions and decomposition, which has hindered the development of stable pharmaceutical compositions, unlike its counterpart 5-formyltetrahydrofolic acid.
Innovation Solution
Adjusting the pH to a basic range (7.5-10.5) with citrate, which forms a synergistic complex that inhibits the separation of formaldehyde from the MTHF molecule, thereby preventing hydrolysis and oxidation, even without the use of reducing agents or exclusion of oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MTHF is used in aqueous solutions for pharmaceutical purposes, then therapeutic effect is achieved, but oxidation and hydrolysis occur leading to decomposition and instability
Solution Approach 1:
The patent changes the pH parameter from neutral/acidic to basic (pH 7.5-10.5), which fundamentally alters the stability characteristics of MTHF. At basic pH, the methylene group is stabilized against hydrolysis and the folate structure against oxidation, transforming the solution from unstable to stable without requiring antioxidants or air exclusion
Solution Approach 2:
Citrate acts as an intermediary substance that forms a synergistic complex with MTHF at basic pH. This citrate-MTHF complex specifically inhibits the separation of formaldehyde from the MTHF molecule, preventing hydrolysis while also protecting against oxidation. The citrate buffer system serves as a mediator that enables stability without direct contact with oxygen or need for reducing agents
2Reliability
If reducing agents or oxygen exclusion methods are used to stabilize MTHF, then oxidation is prevented, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts and eliminates the need for complex stabilization systems (reducing agents, air exclusion devices, inert atmospheres) by identifying a simpler fundamental cause of instability - neutral/acidic pH conditions. By removing this harmful parameter and establishing basic pH as the stable condition, the solution achieves stability through a single parameter change rather than multiple protective measures
Solution Approach 2:
The basic pH condition itself provides the protective effect against oxidation and hydrolysis without requiring external stabilizing agents. The citrate buffer at basic pH creates a self-stabilizing environment where the MTHF structure is inherently protected, eliminating the need for additional reducing agents or complex protection systems
3Productivity
If high concentration of MTHF is used to enhance cytotoxic effect, then therapeutic efficacy improves, but stability deteriorates due to increased decomposition
Solution Approach 1:
By changing the pH parameter to basic conditions (pH 7.5-10.5), the patent creates a stability environment that allows high concentrations of MTHF to be maintained without decomposition. The citrate buffer at basic pH specifically stabilizes the methylene group against hydrolysis and the folate against oxidation, enabling high-concentration formulations that remain stable for extended periods
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 approach significantly stabilizes MTHF in aqueous solutions, suspensions, and solid forms, allowing for high-concentration, stable compositions that maintain stability for extended periods without antioxidants or air exclusion, suitable for parenteral and other administration methods.
Implementation Method 1
Complex formation between citrate and MTHF on the one hand and between citrate and the counterion (salt) of MTHF on the other hand makes a decisive contribution to the stabilization of the methylene group by inhibiting the separation of formaldehyde (hydrolysis) from the MTHF molecule
Implementation Method 2
the stability of MTHF in aqueous solutions, in suspensions and in solid forms such as powders or lyophilisates can be strikingly increased by adjusting to a basic pH... this stabilization occurs even in the absence of a reducing agent
Implementation Method 3
In contrast to 5-formyltetrahydrofolic acid, 5,10-methylenetetrahydrofolic acid in solution is always in equilibrium with formaldehyde and tetrahydrofolic acid (THF)... citrate inhibits the separation of formaldehyde (hydrolysis) from the molecule
Data Source
AI summary
This invention relates to stable pharmaceutical compositions of 5,10-methylene-(6R)-, -(65)- or -(6R,S)-tetrahydrofolate (MTHF), by adjusting to a basic pH and the simultaneous use of citrate. Stabilisation is effected even in the absence of a reducing agent. The present invention is particularly suitable for producing lyophilisation solutions and lyophilisates or dry powders and dry mixtures, since the stable MTHF solutions can be used in high concentrations for filling corresponding vessels such as vials, ampoules, etc. The lyophilisates have a surprisingly long shelf life and are surprisingly stable. They can be reconstituted without problems by adding water or aqueous solutions, and the final clear injection solutions again exhibit excellent stability properties. Moreover, the present invention even makes it possible to prepare difficultly soluble calcium 15 or acidic salts of MTHF in high concentrations and as physiologically compatible isotonic solutions.