Hydrophilic matrix tablets based on hydroxypropylmethylcellulose (HPMC) and other cellulose derivatives rank among dosage forms with retarded effect widely used in contemporary pharmacotherapy. The active ingredient is released from them in dependence on its properties either by dissolution and diffusion, or erosion of the compact. The dissolution profile of the active ingredient can be influenced by variables of formulation and manufacture, e.g. by the type of HPMCemployed, its concentration, other added auxiliary substances, and compression force which is reflected in the strength of tablets.Two drugs with different solubility were used to study the effect of drug solubility on its release frommatrices: well soluble diltiazemiumchloride and badly soluble ibuprofen. Higher solubility of the drug and lower solubility of compacts resulted in more rapid release of the active ingredient. Also lower concentration of HPMCaccelerates the release of both drugs. The effect of the degree of viscosity of the polymer on drug release was not markedly manifested.

        Key words: hydrophilic matrices – hydroxypropylmethylcellulose – drug solubility – strength of tablets – modified release