The polymorphism of cimetidine.

Area of Science:

• Analytical Chemistry
• Solid-State Chemistry
• Pharmaceutical Science

Background:

• Cimetidine exhibits multiple solid-state modifications, leading to nomenclature ambiguity.
• Understanding these polymorphic forms is crucial for pharmaceutical formulation and stability.

Purpose of the Study:

• To resolve nomenclature uncertainties for cimetidine modifications.
• To characterize unknown cimetidine forms using spectroscopic data.
• To rationalize the FT-IR spectral features of different cimetidine polymorphs.

Main Methods:

• High-resolution Fourier Transform Infrared (FT-IR) spectroscopy was employed.
• Analysis was conducted on five known and two uncharacterized cimetidine modifications.
• Chronological publication order and standard nomenclature conventions were used for identification.

Main Results:

• Spectroscopic data were assigned to specific cimetidine modifications.
• Two previously uncharacterized forms of cimetidine were identified and characterized.
• Distinct spectral differences were observed between anhydrous and monohydrate forms.
• Changes during dehydration of monohydrates without melting were analyzed.

Conclusions:

• The study provides a clear spectroscopic basis for identifying and naming cimetidine modifications.
• FT-IR spectroscopy is a powerful tool for differentiating cimetidine polymorphs.
• The findings contribute to a better understanding of cimetidine's solid-state behavior.