title: Optics-based compressibility parameter for pharmaceutical tablets obtained with the aid of the terahertz refractive index.
abstract: The objective of this study is to propose a novel optical compressibility parameter for porous pharmaceutical tablets. This parameter is defined with the aid of the effective refractive index of a tablet that is obtained from non-destructive and contactless terahertz (THz) time-delay transmission measurement. The optical compressibility parameter of two training sets of pharmaceutical tablets with a priori known porosity and mass fraction of a drug was investigated. Both pharmaceutical sets were compressed with one of the most commonly used excipients, namely microcrystalline cellulose (MCC) and drug Indomethacin. The optical compressibility clearly correlates with the skeletal bulk modulus determined by mercury porosimetry and the recently proposed terahertz lumped structural parameter calculated from terahertz measurements. This lumped structural parameter can be used to analyse the pattern of arrangement of excipient and drug particles in porous pharmaceutical tablets. Therefore, we propose that the optical compressibility can serve as a quality parameter of a pharmaceutical tablet corresponding with the skeletal bulk modulus of the porous tablet, which is related to structural arrangement of the powder particles in the tablet.
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland. Electronic address: mousumi.chakraborty@uef.fi.
authors.forename: Mousumi
authors.initials: M
authors.lastname: Chakraborty
authors.affiliation: Omya International AG, CH-4665 Oftringen, Switzerland.
authors.forename: Cathy
authors.initials: C
authors.lastname: Ridgway
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Prince
authors.initials: P
authors.lastname: Bawuah
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Markl
authors.affiliation: Omya International AG, CH-4665 Oftringen, Switzerland; Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, FI-00076 Aalto, Helsinki, Finland.
authors.forename: Patrick A C
authors.initials: PAC
authors.lastname: Gane
authors.affiliation: School of Pharmacy, Promis Centre, University of Eastern Finland, P. O. Box 1617, FI-70211, Kuopio, Finland.
authors.forename: Jarkko
authors.initials: J
authors.lastname: Ketolainen
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, United Kingdom.
authors.forename: J Axel
authors.initials: JA
authors.lastname: Zeitler
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Kai-Erik
authors.initials: KE
authors.lastname: Peiponen
mesh_terms: D002482:Cellulose; D005079:Excipients; D012031:Refractometry; D013607:Tablets; D013678:Technology, Pharmaceutical; D055068:Terahertz Spectroscopy
chemical_list: D005079:Excipients; D013607:Tablets; D002482:Cellulose
keywords: Indomethacin; Microcrystalline cellulose; Optical compressibility; Pharmaceutical tablet; Skeletal bulk modulus; Structural parameter; Terahertz