Formulation and evaluation of methyldopa sustained release matrix tablets

The objective of the present study was to formulate methyldopa sustained release matrix tablets using hydrophilic hydroxypropyl methylcellulose (HPMC) alone or in combination with hydrophobic ethyl cellulose polymer(EC). Matrix tablets were prepared by wet granulation method, and subjected to physiochemical studies. All formulations showed physiochemical properties which appear to be in compliance with pharmacopeial standards. The in-vitro dissolution studies showed that increase in concentration or viscosity of HPMC polymer led to decrease in the rate of drug release decreased. The results also revealed that Combination of HPMC K4M and EC slower drug release more than using HPMC K4M alone. Drug release kinetics of about all formulations correspond best to Korsemeyer-Peppas model and drug release mechanism was anomalous diffusion based on release exponent value.

Preparation and Evaluation of Sustained Release Tablets of Nifedipine Solid Dispersions

Nifedipine is one of the most used calcium channel blocking agents. Due to its low aqueous solubility, it often shows low and irregular bioavailability after oral administration. Nifedipine has short half-life so it has to be administered many times a day. Immediate-release formulations increase the risk of myocardial infarction and mortality. This research aims to prepare dual-function drug delivery system to enhance nifedipine solubility using solid dispersion technique, and extend its release by incorporating these dispersions in matrix tablets. 32 Factorial design was employed; two independent variables, Poloxamer 188 and Ethyl cellulose, to improve solubility and extend release respectively, were used in 3 levels. The prepared tablets were examined, and succeeded in extending nifedipine release up to 12 hrs. The equations that link the dependent and independent variables were obtained, through which tablet hardness and the released amount after 1, 4 and 6 hours could be predicted.