The use of carrageenan in mixture with microcrystalline cellulose and its functionality for making tablets

The modulation of tableting and release behavior of combinations of kappa-carrageenan Gelcarin((R)) GP 911 NF and microcrystalline cellulose (MCC) Avicel((R)) PH 101 has been evaluated. Graded binary mixtures were tableted to a maximum relative density of 0.850 at the maximum displacement of the upper punch. Additionally, ternary mixtures with the same ratios of kappa-carrageenan and MCC and a constant percentage of theophylline monohydrate (20% (v/v)) were tested for their release behavior. Tablets produced from pure kappa-carrageenan deformed more elastically than pure MCC, the tablets produced were stable but not at the same degree as those made from MCC. Scanning electron microscopy (SEM) pictures showed that for MCC a smooth surface of the tablets resulted, tablets made from kappa-carrageenan showed less 'fusion' and thus more mechanical interlocking is responsible for their stability. Binary mixtures showed a continuous change in compaction properties from plastic to elastic deformation. All ternary mixtures with theophylline deformed more plastically than the binary mixtures, the change in deformation properties remained the same. Theophylline reduced the crushing strength due to its different fracture properties. The ternary mixtures showed different release mechanisms: Fast release up to 20% (v/v) kappa-carrageenan, slower release starting from 30% (v/v). The kinetics of release tended at 70% (v/v) more clearly towards zero-order kinetics. This change in release is in accordance with a change in swelling of tablets made of the binary mixtures.