Use of calcium carbonate as an excipient for release of poorly water soluble drugs: The case of carbamazepine

Carbamazepine (CBZ) is a poorly water soluble drug owing to the Biopharmaceutic Classification System (BCS) class II. It is characterized by a variable bioavailability and by the presence of different polymorphs. In this paper the effects of CaCO3 on the physicochemical properties of CBZ and its solubility and release were evaluated. CaCO3 is a naturally non-toxic biomineral and was chosen because it is a safe, cheap and eco-friendly excipient able to dissolve in an acidic environment.


• Composites of CaCO3 and carbamazepine were prepared by milling and antisolvent procedure. 
• Different crystal forms of carbamazepine were obtained and investigated. 
• A solid-state study was carried out to correlate with pharmaceutical properties. 
• Enhancement of drug apparent solubility and release was achieved using CaCO3.

Composites with different CBZ loadings were prepared by ball milling and antisolvent method. The composites were characterized by X-ray powder diffraction, differential scanning calorimetry analysis and attenuated total reflectance FT-IR which revealed that both the presence of CaCO3 and the preparation procedure affect the polymorphic form crystallinity and intermolecular interactions among the drug molecules. Scanning electron microscopy showed that small drug crystals with different crystalline forms were deposited on the surface of the CaCO3 particles. Solubility and dissolution tests showed an increase in the apparent solubility of CBZ and improved drug release. These results demonstrated that CaCO3 affected the drug release properties likely due to its pH-sensitive characteristics. Continue on use of calcium carbonate as an excipient for release of poorly water soluble drugs

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