Formulation and Evaluation of Pulsatile Drug Delivery System of Metoprolol Tartarate Using Core in Cup Tablet

Abstract The purpose of this work is to formu late a pulsatile drug delivery system using metoprolol tartarate as model drug. A core in cup (three component tablet) is prepared where in core tablet, an impermeable material surrounding the tablet except the top and soluble hydrophilic poly mer layer at the top is designed. The core tablet contains metoprolol tartarate, cellu lose acetate propionate is used as impermeable memb rane and sodium alginate 500 cps and sodium alginate 2000 cps used as soluble hydrophilic poly mer layer .The top cover layer is prepared using 3 2 factorial design. Quantification of water uptake, top layer expansion, in-v itro dissolution studies, radial and axial expansion, stereomicroscopic image, and short term stability studies are performed. The concentration of top layer of hydrophilic poly mer is a critical factor governing the release pattern, increase in the concentration increased lag t ime and delay the release .The T70% and T90 % values are also influenced by the polymer concentration with less polymer concentration of hydrophilic poly mer lesser T70% and T90 % values are obtained and as the concentration increased higher values are obtained. It can be concluded from the study that pulsatile drug delivery system useful in chronotherapy of hypertension can be prepared by this technique

Polymeric ocular hydrogels and ophthalmic inserts for controlled release of timolol maleate

Background: Ophthalmic drug delivery systems are the challenging subject for the researchers because of delicate nature of ocular membrane and preventive barriers leading to less than 1 % of Bioavailability. Reasons for reduced bioavailability are due to rapid pre corneal elimination, tear turnover, lacrimal drainage, blinking and degradation by enzymes. Less bioavailability causes short duration of action and increased frequency of administration. Materials and Methods: Timolol maleate was used as model drug. Dynamic drug release studies were used to study the polymeric hydrogels and ophthalmic inserts. Rheological studies were carried out by Brookfield Viscometer LVDV- II+. Result and Discussion: Viscosity value lies in the range of 4.08 to 31.8 cps. Drug release data was fitted to various kinetic equations such as First order plots, Higuchi plots, Peppa′s exponential plots. The results shows fairly linear curve and the slope value of the Peppa′s equation is less than 0.5 and hence follows the fickian diffusion. Conclusion: The developed hydrogels and inserts were therapeutically effacious, stable, non irritant and provide a sustained release of drug over 8 hours time period

Stimuli-sensitive hydrogels: A novel ophthalmic drug delivery system

<b>Background:</b> 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. <b>Aim:</b> 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. <b>Materials and Methods:</b> 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. <i>In vivo</i> study for reduction in intraocular pressure was carried out by using albino rabbits. <b>Statistical Analysis:</b> 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 <i>in vivo</i> study. <b>Results:</b> 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&#x0025; of drug was released in an 8 h drug release study. Sterile hydrogels with no ocular irritation were obtained. <b>Conclusions:</b> Hydrogels show increase in viscosity due to change in pH. Hydrogels were therapeutically effacious, stable, non-irritant and showed Fickian diffusion. <i>In vivo</i> results clearly show a prolonged reduction in intraocular pressure, which was helpful for reduction in the frequency of administration

Hydrogel dressings

Hydrogels are materials with unique properties that allow them to be applied in major aspects of human activities. Modern hydrogel wound dressings are often classified as hydrocolloid dressings, alginate dressings, flat hydrogel dressings, amorphous hydrogel dressings, foam dressings, films, and composite materials composed of a fibrous substrate impregnated with hydrogel forming polymer. This chapter considers several methods used for the production of hydrogel wound dressings by polymerization of monomers and cross‐linking of polymers. Cross‐linking of polymers is a more common way of producing hydrogel wound dressings because it gives an opportunity to avoid contamination of the final product with unreacted toxic or irritating components (monomers and initiator). There are a few cross‐linking techniques that can be used for the production of hydrogel dressings: physical cross‐linking; cross‐linking by low molecular weight compounds; ultraviolet, gamma, and electron beam irradiation; condensation reactions between functional groups of polymers; enzymatic cross‐linking; and interpenetrating polymer network cross‐linking