Design and in-vitro evaluation of sustained release mini-matrices by extrusion

Sustained release mini-matrices (multiple unit dosage form) were developed by means of extrusion, using Diclofenac sodium (DS) as a model drug and ethyl cellulose, hydroxypropyl methylcellulose as matrix materials, with or without channeling agent (lactose) and plasticizer (propylene glycol). Estimation of DS in the prepared mini-matrices was carried out by extracting the drug with methanol and measuring the absorbance at 282.4 nm. The prepared mini-matrices were further evaluated for surface texture by scanning electron microscopy, uniformity of diameter, thickness and weight; moisture content (Karl-Fischer method), in vitro drug release pattern, drug-excipient interaction and short term stability. All the hydroxypropyl methylcellulose mini-matrices displayed nearly zero-order release kinetics from 2-8 hours releasing >85% of the drug. Formulation prepared with a drug-polymer ratio of 1:0.5 (diclofenac sodium: hydroxypropyl methylcellulose) and 5% lactose as channeling agent and 5% propylene glycol (by weight of polymer) as plasticizer showed promising results as a controlled release dosage form and released approximately 99% of the drug in 12 hrs. This study proves that extrusion method can be used for designing controlled release drug delivery systems providing nearly zero-order drug release over a period of 12 hrs.