The effect of Al3+on the propranolol hydrochloride release from polyanionic polymer matrices

Sustaining propranolol hydrochloride (PLH) decreases its frequency of daily dosage, side effects and enhances patientcompliance. In order to control the release of PLH the effect of Al3+ and type of anionic polymer on the drug release was studied. Matrices of sodium carboxymethyl cellulose(NaCMC), sodium alginate(NaAlg) and tragacant(Trag) containing drug as well as different amounts of Al3+ were prepared and the drug release was measured in distilled water using USP I dissolution tester. Concentration of dissolved drug was assayed spectrophotometrically. The release of different matrices was compared with the aid of some model independent parameters e.g. F360' (drug fraction released in 3 ') and model dependent parameters. Various amounts of Al3+ had different effects. In the range of 0-0.125 milli equivalen (meq) Al3+ in NaCMC matrices the F360' was reduced from 0.63 to 0.21 via in situ crosslinking between Al3+ and polymer and in the higher ranges e.g. 0.5 meq the release increased to 0.79 probably through disintegrating effect of Al3+. A similar effect was seen for NaAlg matrices. Al3+ had very little influence on the release of Trag matrices. Analysis by kinetic models indicated complex mechanisms such as water penetration, diffusion, erosion, dissolution, cross linking and disintegration. With the choice of the most suitable anionic polymer (NaCMC) together with given amount of Al3+ the release of PLH from matrices can be controlled at any desired rate. Matrices of NaAlg were the next suitable formulations. However, Trag was not a suitable polymer because it did not produce appreciable cross linkage with Al3+