RESUMO
Recently there has been greater interest in modified release systems like extended release or delayed release systems to deliver required amount of drug at specific site for duration of therapy. These systems play an important role in the chronotherapy of asthma, angina and arthritis. In the present study fast disintegrating core tablets of model drug diclofenac sodium were coated with coating material granules containing okra mucilage or modified okra mucilage in combination with HPMC K15M and evaluated for pre and post compression parameters. The in-vitro disintegration time for core tablets was 64.66±0.577 sec and the wetting time was 41.66 ±0.57 sec. All other parameters were satisfactory for core and coated formulations. Formulations P1, P2 and P3 showed drug release of 96.789 ± 0.66994 %, 100.86 ± 0.42729 % and 95.15 ±0.7180 % in 24 hrs respectively. The prepared formulations showed greater drug release after 6 hrs indicating a burst release in intestinal environment, making the formulations suitable candidates for colonic drug release. All the prepared formulations followed first order kinetics with release exponent n>1.There was no significant difference in in-vitro dissolution in presence and absence of rat caecal content indicating drug release depends on pH, swelling and erosion.
RESUMO
Background: Stimuli-sensitive hydrogels are three-dimensional, hydrophilic, polymeric networks capable of imbibing large amounts of water or biological fluids on stimulation, such as pH, temperature and ionic change. Aim: To develop hydrogels that are sensitive to stimuli, i.e. pH, in the cul-de-sac of the eye for providing a prolonged effect and increased bioavailability with reduction in frequency of administration. Materials and Methods: Hydrogels were formulated by using timolol maleate as the model drug, polyacrylic acid as the gelling agents, hydroxyl ethyl cellulose as the viscolizer and sodium chloride as the isotonic agent. Stirring of ingredients in pH 4 phosphate buffer at high speed was carried out. The dynamic dialysis technique was used for drug release studies. In vivo study for reduction in intraocular pressure was carried out by using albino rabbits. Statistical Analysis: Drug release studies data were used for statistical analysis in first-order plots, Higuchi plots and Peppas exponential plots. Student t-test was performed for in vivo study. Results: Viscosity of the hydrogel increases from 3.84 cps to 9.54 cps due to change in pH 4 to pH 7.4. The slope value of the Peppas equation was found to be 0.3081, 0.3743 and 0.2964. Up to 80% of drug was released in an 8 h drug release study. Sterile hydrogels with no ocular irritation were obtained. Conclusions: Hydrogels show increase in viscosity due to change in pH. Hydrogels were therapeutically effacious, stable, non-irritant and showed Fickian diffusion. In vivo results clearly show a prolonged reduction in intraocular pressure, which was helpful for reduction in the frequency of administration.