Abstract
Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography. Terahertz time-domain spectroscopy was used to derive the porosity using effective medium approximations, that is, the traditional and an anisotropic Bruggeman model. The anisotropic Bruggeman model yields the better correlation with the nominal porosity (R2 = 0.995) and it provided additional information about the shape and orientation of the pores within the powder compact. The spheroidal (ellipsoids of revolution) shaped pores have a preferred orientation perpendicular to the compaction direction causing an anisotropic behavior of the dielectric porous medium. The results from X-ray computed microtomography confirmed the nonspherical shape and the orientation of the pores, and it further revealed that the anisotropic behavior is mainly caused by the interparticle pores. The information from both techniques provides a detailed insight into the pore structure of pharmaceutical tablets. This is of great interest to study the impact of tablet microstructure on the disintegration and dissolution performance.
Highlights
Overall in the pharmaceutical market, tablets continue to be the most convenient way to deliver an active pharmaceutical ingredient (API) to the patient
High porosities are desirable as the pore structure of a tablet have strong impact on the liquid penetration in a tablet, which is in the majority of cases the limiting step during disintegration
A typical pharmaceutical functionalized calcium carbonate (FCC) particle consists of a calcium carbonate/hydroxyapatite ratio of 15%-20%
Summary
Overall in the pharmaceutical market, tablets continue to be the most convenient way to deliver an active pharmaceutical ingredient (API) to the patient. D. Markl et al / Journal of Pharmaceutical Sciences 106 (2017) 1586-1595 functionality, MCC absorbs water, both into the interparticulate pore structure[3,4] and by diffusion into the cellulose intraparticle space.[5] Together with the excellent surface wetting properties by water, this makes MCC an excipient for a broad spectrum of applications ranging from orally dispersible tablets[6] to controlled drug delivery.[7] its use in orally dispersible tablets is constrained due to its limited capability of achieving tablet porosities >40%. Effective disintegration of a tablet is, critical in maximizing the exposure time of the API to gastric and intestinal fluids so that the API can be absorbed at higher rates, leading to increased bioavailability and a faster onset of the desired pharmacologic effect
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