RESUMEN
The objective of the present study was to evaluate the effect of different plasticizers on the ethylcellulose coatings of capsules and its timed release characteristics. Various plasticizers such as dibutyl phthalate (DBP), triacetin (TA), glycerol, triethyl citrate (TEC), polyethylene glycol-4000 and polyethylene glycol-6000 (PEG) were studied. The physicochemical properties of the casted polymeric films such as mechanical resistance, water uptake and dry weight loss were determined. Also the type and concentration of plasticizer on timed release of the capsule was studied. The drug release was found to be strongly dependent on the type of plasticizer and was in the order of GY>TA>PEG 6000>PEG 4000>TEC>DBP. Capsules coated with hydrophobic DBP (5%) showed good release with a lag time of 6 ± 0.5 h. DBP provided mechanically resistant coatings on the capsule and remained within the polymeric films without leaching upon exposure to the release media which helped in maintaining the lag time.