Development and Evaluation of Hydrophilic Colloid Matrix of Famotidine Tablets

The objective of the present study was to develop a once-daily sustained-release (SR) matrix tablet of famotidine. Nine different formulations (F1–F9) were prepared by direct compression method using Avicel PH101 as filler/binder in the range of 41–27% in F1–F3, 18–22% in F4–F7, and 16–18% in F8–F9 and hydroxypropyl methylcellulose (4,000 cps) as hydrophilic matrix was used in F1–F3 from 19% to 30%, around 40% in F4–F7, and 42–45% in F8–F9. Talc and Aerosil were added in the ratio of 0.7–1.2%. The tablets were subjected to various physical parameters including weight variation test, hardness, thickness, diameter, friability, and in vitro release studies. Assay was also performed according to the USP 30 NF 25 procedure. The results of the physical parameters and assay were found to be within the acceptable range. In vitro dissolution results indicated that formulation F4–F7, having around 40% of rate control polymer, produced a SR pattern throughout 24 h. F1–F3 showed drug release at a faster rate, while F8–F9 released much slower, i.e., <80% in 24 h. Model-dependent and model-independent methods were used for data analysis and the best results were observed for F4 in zero order (r2 = 0.984) and F6 in Korsmeyer and Higuchi (r2 = 0.992 and 0.988). The parameter n indicated anomalous diffusion, while β in Weibull showed a parabolic curve with higher initial slope. The f2 similarity test was performed taking F4 as a reference formulation. Only the F5–F7 formulations were similar to the reference formulation F4. The mean dissolution time was around 10 h for the successful formulation

Effects of Added Surfactant on Swelling and Molecular Transport in Drug-Loaded Tablets Based on Hydrophobically Modified Poly(acrylic acid)

A combination of NMR chemical shift imaging and self-diffusion experiments is shown to give a detailed molecular picture of the events that occur when tablets of hydrophobically modified poly(acrylic acid) loaded with a drug (griseofulvin) swell in water in the presence or absence of surfactant (sodium octylbenzenesulfonate). The hydrophobic substituents on the polymer bind and trap the surfactant molecules in mixed micelles, leading to a slow effective surfactant transport that occurs via a small fraction of individually dissolved surfactant molecules in the water domain. Because of the efficient binding of surfactant, the penetrating water is found to diffuse past the penetrating surfactant into the polymer matrix, pushing the surfactant front outward as the matrix swells. The added surfactant has little effect on the transport of drug because both undissolved solid drug and surfactant-solubilized drug function as reservoirs that essentially follow the polymer as it swells. However, the added surfactant nevertheless has a strong indirect effect on the release of griseofulvin, through the effect of the surfactant on the solubility and erosion of the polymer matrix. The surfactant effectively solubilizes the hydrophobically modified polymer, making it fully miscible with water, leading to a more pronounced swelling and a slower erosion of the polymer matrix