Solvent-Assisted Secondary Drying of Spray-Dried Polymers.

Area of Science:

• Pharmaceutical Sciences
• Chemical Engineering
• Materials Science

Background:

• Spray-drying is crucial for creating amorphous solid dispersions to improve drug bioavailability.
• Residual solvents in spray-dried products necessitate secondary drying, which can be time-consuming.
• Traditional secondary drying methods pose challenges in balancing process time and product stability.

Purpose of the Study:

• To introduce and evaluate solvent-assisted secondary drying for accelerated residual solvent removal.
• To compare methanol-assisted drying with vacuum-only and water-assisted drying techniques.
• To optimize the secondary drying process for spray-dried amorphous solid dispersions.

Main Methods:

• Spray-dried polymers were subjected to secondary drying using three methods: vacuum-only, water-assisted, and methanol-assisted.
• A jacketed, agitated-vessel dryer was employed for all drying experiments.
• Residual solvent content was monitored over time using gas chromatography (GC) and Karl Fischer (KF) titration.

Main Results:

• Methanol-assisted drying demonstrated superior performance in residual solvent removal compared to vacuum-only and water-assisted methods.
• The effectiveness of methanol-assisted drying was observed across model systems known for slow secondary drying.
• All studied cases showed that methanol-assisted drying outperformed the other techniques.

Conclusions:

• Methanol-assisted drying is a highly effective technique for accelerating residual solvent removal from spray-dried materials.
• The enhanced diffusion of methanol aligns with the free-volume theory of solvent diffusion in polymers.
• This method offers a promising alternative for efficient secondary drying in pharmaceutical manufacturing.