Abstract
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.
Highlights
In the pharmaceutical industry, the most popular method of drug formulation is in the solid form or crystalline form and it has a definite arrangement of atoms having long range order and is highly stable
Recent studies show that molecular mobility is the key factor responsible for the devitrification of the drug in the amorphous form and devitrification can occur even below the glass transition temperature (Tg)
We studied the dielectric properties of supercooled cimetidine above the glass transition temperatue
Summary
The most popular method of drug formulation is in the solid form or crystalline form and it has a definite arrangement of atoms having long range order and is highly stable. They have high molecular mobility which will reduce the shelf-life of the drugs during processing, handling and storage [3]. Recent studies show that molecular mobility is the key factor responsible for the devitrification of the drug in the amorphous form and devitrification can occur even below the glass transition temperature (Tg).
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