Interpolyelectrolyte complexation between carboxymethyl-kappa-carrageenan (CMKC, and Eudragit RL 30D (ERL) was studied and characterized. The obtained polyelectrolyte complex (PEC) was used to develop bioadhesive matrix tablets aimed to prolong buccal-residence time and sustain drug delivery. The optimum ERL-CMKC complexation weight ratio (7:3) was determined in distilled water using apparent viscosity and turbidity measurements. PEG properties were determined by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction and scanning electron microscopy (SEM). Miconazole matrix tablets were prepared by direct compression. Swelling properties and drug release in phosphate buffer solution medium (PBS, pH 6.8) were reported. Tablets exhibited extremely high swelling properties whereas; the dissolution data were fitted to different dissolution models. The drug release from matrix systems depends on the PEG concentration's and approaches zero order kinetics. Drug release mechanism is controlled by the superposition of diffusion and erosion. The relaxation phenomenon appears to increase along the release process and even overcomes diffusion for some systems. A PEC's optimal proportion of 65.06% in the tablet formula provides a dissolution profile characterized by Korsmeyer-Peppas exponent value (n) exceeding 0.97. The ERL-CMKC polyelectrolyte complex has demonstrated a high potential as an excipient for the production of swellable matrix systems with sustained drug release properties. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.