Development and Evaluation of Press Coated Time-Release Tablet of Nifedipine

The aim of the study was to develop press coated time release tablets of nifedipine, from which the drug is released in a controlled manner to suite the Chronotherapeutics of the disease i.e., hypertension. The tablets, each consisting of a core and a coat, were prepared using compression coating technique. Core tablet was immediate-release formulation containing nifedipine soild dispersion of 1: 2 ratio with mannitol to enhance its solubility. The core tablet was then coated with a mixture of rate controlling polymers like polyethylene glycol (PEG6000) and hydroxyl propyl methyl cellulose (HPMC K100M) in different ratios to produce time release tablets of nifedipine. The core and press-coated tablets were evaluated for their physico-chemical properties, in-vitro release and stability studies. The in vitro drug release pattern indicated that type of polymer and its concentration had marked influence on the drug release from tablets. The drug release decreased with increasing amounts of HPMC K100M in the formulation. A lag time of 2 to 6 hrs was achieved with the polymers used. 2% sodium lauryl sulphate (SLS) was added as dissolution enhancer for dissolution study. The mechanism of drug release from all the press-coated tablets followed Higuchi model release kinetics with r² value 0.983 to 0.997. FT-IR and DSC studies revealed no chemical interaction between drug and polymers used.