Understanding and Solving TXC (Tranexamic Acid) Solubility Issues

It sounds like you are working with Tranexamic Acid (TXC) and encountering a common solubility challenge in your formulation.

What is happening?

1. Solubility in Hot Butylene Glycol: Tranexamic Acid has increased solubility in glycols like Butylene Glycol at higher temperatures (60-70°C). This is why it dissolves completely when heated.
2. Decreased Solubility on Cooling: As the temperature drops, the solubility of Tranexamic Acid in Butylene Glycol decreases.
3. Precipitation with Water: Tranexamic Acid is highly soluble in water. However, when you add water to the cooled Butylene Glycol/Tranexamic Acid mixture, you create a mixed solvent system. With only 6% Butylene Glycol and the rest being water, the concentration of Butylene Glycol is likely too low to act as an effective co-solvent to keep 2% Tranexamic Acid dissolved in the final formulation at room temperature. The Tranexamic Acid then precipitates out, causing the cloudiness and undissolved particles.

How to fix it?

The most effective and recommended method for incorporating Tranexamic Acid into a formulation is to dissolve it directly into the water phase.

• Dissolve in Water First: Add the 2% Tranexamic Acid to your formulation's water phase. Stir until it is completely dissolved. Tranexamic Acid dissolves readily in water, often at room temperature, but gentle warming (e.g., 40-50°C) can speed up the process if needed.
• Once the Tranexamic Acid is fully dissolved in the water phase, you can then proceed to add the Butylene Glycol and other ingredients according to your formula steps.

This method ensures that the Tranexamic Acid is fully dissolved in the solvent it is most soluble in (water) before being combined with other ingredients, preventing precipitation issues in the final product.

Ensure your final formulation's pH is within the optimal range for Tranexamic Acid (typically pH 3-8) for stability.