DESCRIPTION AND VALIDATION OF AN APPARATUS FOR GEL STRENGTH MEASUREMENTS

The increasing interest in gel-like dosage forms and in systems that undergo gelification upon contact with biological fluids (like hydrogels and hydrophilic swellable matrices) suggests the importance of gel strength measurements. For example, it has been suggested that the strength rather than the viscosity of the gel layer plays a major role in drug release from hydrophilic matrices. Nevertheless, probably due to the lack of a user-friendly and suitable apparatus, the gel strength parameter is not routinely investigated in preformulation and formulation studies of such dosage forms. In the present work, an apparatus, which had been previously designed for the characterisation of industrial polymers, was modified to make it suitable for measuring the gel strength of pharmaceutical systems and its performance was validated under differing experimental conditions. The results of gel strength measurements effected on hydroxypropylmethylcellulose solutions and on kappa-carrageenan and carboxyvinyl polymer gels are reported herein.