Assessing the re-crystallization behaviour of amorphous lactose using the RH-perfusion cell

Area of Science:

• Physical Chemistry
• Materials Science
• Pharmaceutical Sciences

Background:

• Lactose crystallization is crucial in pharmaceutical formulations.
• Limited research exists on alpha-lactose monohydrate and beta-lactose formation during lactose recrystallization.
• Previous studies used static methods, lacking dynamic humidity control.

Purpose of the Study:

• To investigate the recrystallization behavior of amorphous lactose and its mixtures using a novel microcalorimetric technique.
• To determine the influence of different lactose carriers (alpha-lactose monohydrate, beta-lactose) on recrystallization.
• To differentiate between monohydrate and anhydrous lactose formation based on desorption enthalpy.

Main Methods:

• Utilized a relative humidity-perfusion cell (RH-perfusion cell) for controlled humidified air delivery.
• Investigated purely amorphous lactose and powder mixtures with varying amorphous lactose concentrations.
• Employed solution calorimetry to confirm findings from RH-perfusion cell experiments.

Main Results:

• Pure amorphous lactose showed high beta-lactose formation at 60-80% RH.
• Mixtures with alpha-lactose monohydrate as a carrier exhibited similar high beta-lactose content.
• Mixtures with beta-lactose as a carrier formed less beta-lactose; only alpha-lactose monohydrate formed at 90% RH.

Conclusions:

• Recrystallization behavior differs significantly based on the carrier used (alpha-lactose monohydrate vs. beta-lactose).
• Relative humidity plays a critical role in determining the crystalline form of re-crystallized lactose.
• The RH-perfusion cell is effective for studying lactose recrystallization dynamics.