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BioMed Research International
Volume 2014 (2014), Article ID 671532, 8 pages
Research Article

Drug Release Kinetics and Front Movement in Matrix Tablets Containing Diltiazem or Metoprolol/λ-Carrageenan Complexes

1Department of Pharmacy, University of Parma, Parco delle Scienze 27/A, 43124 Parma, Italy
2Department of Drug Sciences, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
3Eratech Srl, Via Gandine 4, 29121 Piacenza, Italy

Received 26 February 2014; Revised 8 May 2014; Accepted 28 May 2014; Published 19 June 2014

Academic Editor: Shirui Mao

Copyright © 2014 Ruggero Bettini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In this work we investigated the moving boundaries and the associated drug release kinetics in matrix tablets prepared with two complexes between λ-carrageenan and two soluble model drugs, namely, diltiazem HCl and metoprolol tartrate aiming at clarifying the role played by drug/polymer interaction on the water uptake, swelling, drug dissolution, and drug release performance of the matrix. The two studied complexes released the drug with different mechanism indicating two different drug/polymer interaction strengths. The comparison between the drug release behaviour of the complexes and the relevant physical mixtures indicates that diltiazem gave rise to a less soluble and more stable complex with carrageenan than metoprolol. The less stable metoprolol complex afforded an erodible matrix, whereas the stronger interaction between diltiazem and carrageenan resulted in a poorly soluble, slowly dissolving matrix. It was concluded that the different stability of the studied complexes affords two distinct drug delivery systems: in the case of MTP, the dissociation of the complex, as a consequence of the interaction with water, affords a classical soluble matrix type delivery system; in the case of DTZ, the dissolving/diffusing species is the complex itself because of the very strong interaction between the drug and the polymer.