methylcellulose and buflomedil

Previous studies of hydroxypropyl methylcellulose (HPMC)-based tablet during exposure to water showed a number of 'fronts' moving into the tablet but led to contradictory interpretations. These fronts are related to water penetration into and dissolution of the tablet, but the exact nature can not be derived from visible photographic evidence. A method to study tablet dissolution simultaneously by Fourier transform infrared-attenuated total reflection (FTIR-ATR) imaging and macro-photography can assist in providing correct interpretation of the observed fronts.. Therefore, the combination of macro-photography and FTIR-ATR spectroscopic imaging was developed and used to interpret the physical changes leading to the observed fronts. Buflomedyl pyridoxal phosphate (BPP), a coloured drug, was used as a model drug.. The quantitative results obtained by FTIR-ATR imaging enabled the attribution of the three observed fronts (inside to outside) to: (1) true water penetration, possibly combined with (partial) dissolution of buflomedyl pyridoxal phosphate (BPP); (2) total gellification of HPMC; (3) erosion front.. The method to study dissolution of a tablet simultaneously by FTIR-ATR imaging and macro-photography has been developed and used to obtain reliable interpretation of the fronts observed during tablet dissolution.

Topics: Drug Carriers; Hypromellose Derivatives; Image Interpretation, Computer-Assisted; Interferometry; Light; Methylcellulose; Photography; Pyrrolidines; Reproducibility of Results; Solubility; Spectroscopy, Fourier Transform Infrared; Tablets; Technology, Pharmaceutical; Time Factors; Water

The aim of this work was to study the release mechanisms of drugs having different solubility (buflomedil pyridoxalphosphate 65%, sodium diclofenac 3.1%, nitrofutantoin 0.02% w/v,) from hydroxypropyl methylcellulose (HPMC) matrices by concomitantly studying swelling, diffusion and erosion fronts movement and drug delivery. The main goal was to clarify the role played by polymer swelling in drug transport. The results showed that the rate and amount of drug released from swellable matrices was dependent not only from drug dissolution and diffusion but also from solid drug translocation in the gel due to polymer swelling. In fact, as drug solubility decreased, the slower drug dissolution rate in the gel layer allowed drug particles to be transported close to the matrix erosion front. The presence of solid particles in the gel reduced the swelling and the entanglement of polymer chains and affected the resistance of gel towards erosion. As a consequence, the matrix became more erodible. The erosive delivery accelerated after the matrix had been completely transformed into the rubbery state, particularly when a considerable amount of solid drug particles remained in the gel phase.

Topics: Diclofenac; Drug Delivery Systems; Gels; Lactose; Methylcellulose; Nitrofurantoin; Oxazines; Pyrrolidines; Solubility

In the present work, the drug volume fraction profiles of a colored and very soluble drug, buflomedil pyridoxal phosphate, in the gel layer of initially glassy hydroxypropylmethyl cellulose matrices were studied, using image analysis of pictures of the matrices during swelling and release. The goal was to correlate the drug release kinetics with the dynamic behavior of the drug gradient in the gel layer. An inert (nonswellable) matrix, manufactured by substituting hydroxypropylmethyl cellulose with an inert polymer and containing the same amount of buflomedil pyridoxal phosphate, was prepared as well. The drug color gradient in the partially extracted region and the flux of this matrix were compared to the swellable matrix. The drug gradient in the dissolved drug gel layer of swellable matrices was observed. It was demonstrated that drug release kinetics does not only depend on drug diffusion and matrix erosion, but also on drug dissolution in the gel and on polymer relaxation.

Topics: Diffusion; Drug Carriers; Drug Delivery Systems; Hypromellose Derivatives; Kinetics; Methylcellulose; Models, Biological; Pyrrolidines; Solubility

Swellable controlled release devices of buflomedil pyridoxalphosphate in hydroxypropyl methylcellulose were prepared, and their swelling and release behavior was investigated. The drug release as a function of time was investigated for various system parameters. Three distinct fronts were observed during the swelling and release processes, i.e., a swelling, a drug diffusion, and an erosion front. The drug diffusion front could be readily determined due to the drug's yellow color. The relative positions of the fronts and the drug release rate were studied as functions of the initial porosity and the molecular weight of the polymer carrier. It was shown that the drug diffusion front best describes the overall release behavior of the system. The fractional drug release was a strong function of the dissolved drug gel layer thickness, which separates the diffusion front from the erosion front. The effect of drug solubility was also investigated by altering the pH and the ionic strength of the dissolution medium. It was shown that as drug solubility increased, the undissolved drug gel layer thickness decreased, again showing the importance of the movement of the diffusion front in controlling the overall release.

Topics: Delayed-Action Preparations; Diffusion; Hydrogen-Ion Concentration; Hypromellose Derivatives; Kinetics; Methylcellulose; Molecular Weight; Pyrrolidines; Solubility; Spectrophotometry, Ultraviolet; Tablets; Viscosity