Succinylsulfathiazole crystal forms. III: Crystal growth studies

Area of Science:

• Solid-state chemistry
• Pharmaceutical sciences
• Crystallization

Background:

• Succinylsulfathiazole exists in different crystal forms, including anhydrous Form I and a stable dihydrate Form II.
• Understanding crystal form transformation is crucial for pharmaceutical formulation and stability.

Purpose of the Study:

• To investigate crystal growth during the transformation of succinylsulfathiazole crystal forms in aqueous suspensions.
• To examine the influence of physical conditions and additives on this transformation and subsequent crystal growth.

Main Methods:

• Projecting microscopy was used to observe crystal growth in aqueous suspensions.
• Particle-size distribution of succinylsulfathiazole Form I was analyzed under various conditions.
• Rates of crystal growth were quantified by measuring the increase in particle diameter over time.

Main Results:

• Increased temperature, agitation, and seeding with Form II accelerated the crystal growth of Form I.
• Sulfathiazole and polysorbate 80 exhibited growth-retarding effects.
• Methylcellulose significantly inhibited crystal growth for over a year, while Form II suspensions remained stable.

Conclusions:

• Crystal growth observed is a direct result of the succinylsulfathiazole crystal form transformation.
• Physical parameters and specific additives can significantly modulate the rate of this transformation and crystal growth.