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Fragility of Cimetidine Drug Probed by Broadband Dielectric Spectroscopy

Sailaja U and Shahin Thayyil M

Cimetidine is a histamine H2-receptor antagonist that inhibits stomach acid production. It is largely used in the treatment of heartburn and peptic ulcers. One of the promising methods to improve the solubility and bioavailability of an active pharmaceutical ingredient is the amorphous phase which will have high free energy than that of the crystalline phase. The relaxation dynamics of cimetidine above the glass transition temperature has been studied by Broadband Dielectric Spectroscopy. Dielectric measurements of amorphous cimetidine were performed after its vitrification by fast cooling from few degrees above the melting point (412.50K). The relaxation processes observed above the glass transition temperature, were labeled as alpha and characterized. The temperature dependence of the structural relaxation time can be described over the entire measured range by single Vogel-Fulcher-Tamman (VFT) equation. From the VFT fits, the glass transition temperature was estimated as 316.27 K and a fragility or steepness index as 69, showing that cimetidine is an intermediate glass former.