Characterization of amorphous ursodeoxycholic acid prepared by spray-drying

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Physical Chemistry

Background:

• Ursodeoxycholic acid (UDCA) is a therapeutic bile acid.
• Controlling the solid-state properties, such as crystallinity, is crucial for drug formulation and efficacy.
• Spray-drying is a common technique for producing amorphous forms of active pharmaceutical ingredients.

Purpose of the Study:

• To characterize the amorphous state of UDCA prepared by spray-drying.
• To evaluate the utility of thermal analysis and water vapor adsorption for assessing UDCA crystallinity.

Main Methods:

• Spray-drying of UDCA solutions.
• Characterization using powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, isothermal microcalorimetry, differential scanning calorimetry (DSC), and water vapor adsorption.
• Crystallinity assessment using Ruland's method.

Main Results:

• Spray-drying conditions, particularly inlet-air temperature, influenced UDCA crystallinity.
• Dissolution enthalpy changed from endothermic to exothermic with increasing inlet-air temperature.
• Strong correlations were found between heat of solution, heat of crystallization (DSC), and crystallinity (PXRD).
• Water vapor adsorption increased with temperature, indicating hydrogen bonding in amorphous UDCA.

Conclusions:

• Spray-drying allows for the preparation of UDCA with tunable crystallinity.
• Thermal analysis and water vapor adsorption are reliable methods for evaluating the crystallinity of solid substances like UDCA.
• These techniques can provide valuable insights into the solid-state characteristics of amorphous materials.