Characterization of Polymorphic Forms of Rifaximin

Area of Science:

• Pharmaceutical Sciences
• Solid-State Chemistry

Background:

• Rifaximin is a gut-selective oral antimicrobial with established therapeutic uses.
• The crystalline form (α) exhibits minimal systemic absorption, unlike amorphous forms.
• Polymorphism in drugs can significantly impact bioavailability and therapeutic efficacy.

Purpose of the Study:

• To obtain novel polymorphic forms of rifaximin through recrystallization.
• To characterize these new forms using various analytical techniques.
• To underscore the importance of polymorph analysis in pharmaceutical manufacturing.

Main Methods:

• Recrystallization processes were employed to isolate rifaximin polymorphs.
• Characterization involved thermal analysis, X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM).
• Solubility testing was conducted to assess the physical properties of the obtained forms.

Main Results:

• Six distinct polymorphic forms of rifaximin, designated I-VI, were successfully obtained.
• Characterization confirmed the unique crystalline structures of these new forms.
• Variations in physical properties among the polymorphic forms were observed.

Conclusions:

• The study successfully generated and characterized six new polymorphic forms of rifaximin.
• These findings emphasize the critical need for stringent regulatory requirements for polymorph analysis in drug manufacturing.
• Collaborative efforts between industry and academia are crucial for advancing solid-state drug research.