Low density porous carrier drug adsorption and release study by response surface methodology using different solvents

Low density porous carriers are widely used in the pharmaceutical applications. Response surface methodology, using 3(2) factorial design was used to study drug adsorption on and its release patterns from microporous polypropylene (Accurel MP 1000) in the absence of additives. Ibuprofen, as model drug, was adsorbed on the polymer by solvent evaporation using two organic solvents methanol (M) and dichloromethane (DCM). The amount of carrier (100 mg) and its particle size range (250-350 microm) were kept invariant while solvent volume (X1) and drug amount (X2) were taken as variables. Drug adsorption pattern depended on the type and amount of solvent used. DSC, XRD, FTIR and TGA, predict crystalline nature and physical form of adsorption. SEM showed the penetration and adsorption of the drug in and on the microporous polymer. Accurel MP 1000 had a pore volume of 1.992 g/cm3 and surface area of 55.9855 m2/g as detected by mercury porosimetery. On drug adsorption, pore volume ranged from 0.413 to 1.198 g/cm3 for methanol and 0.280-0.759 g/cm3 for DCM. Similarly surface area was in the range 38.445-25.497 m2/g for methanol and 18.710-32.528m2/g for DCM. The drug release was investigated in phosphate buffer pH 7.2. All batches showed excellent in vitro floating property. Drug release was partial with recovery to complete dependent on type and volume of solvent. R2 values relating to bulk density, pore volume, surface area and drug release at 60, 120 and 180 min were estimated. Effect of solvent properties shows a positive influence on drug adsorption and release. Release profiles of some batches could be considered as gastroretentive drug delivery system.