Study of the rate of drug release from coated cholestyramine-ibuprofen complexes with ethylcellulose and polyethylene glycol 4000

Ibuprofen, is one of the non-steroidal anti-inflammatory drugs (NSAIDs) that due to its higher efficiency and less side effects (as compared with other NSAIDs), is widely used specially for children, but its short half life (1.8-2 hours) and requiring to multiple dosing makes it a good candidate drug for sustained release dosage forms. In this study, Ion-exchange resin system was used to achieve this aim. Ibuprofen was loaded on cholestyramine (an anionic exchanger resin), using a batch method. The resin-drug complex was encapsulated with different amounts of either ethyl cellulose 10cps or 100cps (as a wall – forming agent), by using a solvent evaporation technique. Fractional coat, drug content and drug release rate were determined. Different amounts of polyethylene glycol 4000 (PEG 4000), by using pretreatment method were added to the microencapsulation formula which had the lowest release rate and the later tests were done. The mean amount of drug loaded on resin was 44.8% ± 0.81%. The In vitro release data showed that ethyl cellulose 100cps (EC 100) could not slow release rate of drug and release from these microcapsules, similar to uncoated complex, occurred via particle diffusion (Bt) model. But ethyl cellulose 10cps (EC10), had a significant inhibitory effect on drug release rate. The lowest release rate was obtained from microcapsules with 30% EC10 (C30). PEG4000 caused an increase in the rate of drug release from EC1 coated complexes. All EC10 coated Formulations (with or without PEG4000) except for (C30) followed a square root of time model, the excepted kinetics for homogeneous and granular matrix systems. The most desirable release profile was obtained from C30 formulation which showed a zero order kinetics. Based on the mentioned results EC10 can produce more uniform film than EC100 which has stronger cohesion force. Because of hydrophilicity of PEG 4000, it acts as a channeling agent. In dissolution medium it dissolves out of the microcapsules and leaves channels in EC10 film, from which drug can be released more rapidly.