Evaluations of the Effect of Sodium Metabisulphite on the Stability and Dissolution Rates of Various Model Drugs from the Extended Release Polyethylene Oxide Matrices

This study examines the effect of sodium metabisulphite (SMB) as an antioxidant on the stability and release of various model drugs, namely, propranolol HCl, theophylline and zonisamide from the polyethylene oxide (PEO) tablets. The antioxidant was used to minimise degradation and instability of the manufactured tablets when stored at 40 A degrees C (55 +/- 5% RH) over 8 weeks. Multiple batches of tablets weighing 240 mg (50% w/w) with a ratio of 1:1 drug/polymer and 1% (w/w) sodium metabisulphite containing different model drugs and various molecular weights of PEO 750 and 303 were produced. The results indicated that the use of sodium metabisulphite marginally assisted in reducing drug release and degradation via oxidation in propranolol HCl tablets containing both PEO 750 and 303. In the case of poorly and semi-soluble drugs (zonisamide and theophylline), the formulations with both PEO showed entirely superimposable phenomenon and different release profiles compared to control samples (matrices without SMB). DSC study demonstrated the modifications of the polymer due to degradation and observed the effect of SMB on the thermal degradation of the PEO matrices. The use of antioxidant has assisted in retaining the stability of the manufactured tablets with different model drugs especially those with the highly soluble drug that are susceptible to rapid degradation. This has been reflected by an extended release profile of various drugs used at various stages of the storage time up to 8 weeks.