Formulation of Sustained-Release Matrix Tablets Using Cross-linked Karaya Gum

Purpose: To develop sustained release matrix tablets of diltiazem hydrochloride (DTZ) using modified karaya gum (MK). Methods: MK was prepared by cross-linking karaya gum with tri-sodium tri-metaphosphate (STMP) which was used as a cross linker. Matrix tablets of DTZ were prepared using varying ratios of unmodified karaya gum (K) and MK by direct compression. The matrix tablets were evaluated for pharmacotechnical properties and in vitro release. The optimized formulation was compared with a reference, Dilzem® SR. MK and the formulations were also characterized by scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR) and differential scanning calorimetry (DSC). Results: Tablets formulated with MK showed higher mean dissolution time (MDT) and lower dissolution efficiency than those prepared with karaya gum. Drug release was by water uptake, diffusion and erosion mechanisms. Drug release for tablets prepared with pure K was 99.9 % at the end of 10 h while that tablet made with MK was 68.2 % at the end of 12 h. MK sufficiently controlled the drug release unlike K which exhibited rapid drug release efficiency. SEM images of the tablets before and after dissolution showed some morphological changes on the tablet surface while FTIR and DSC thermogram studies confirmed that there was no chemical interaction between the drug and the polymers in MK formulation. Formulation F6 compared well with Dilzem® SR (reference) (p