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Biomedical subjects

M C Bonferoni

Publications and source records attributed to M C Bonferoni.

23 records · Page 2Linked to original sources
PubMed1989

Swelling-restricted minimatrices for controlled release of drugs. Preliminary in-vivo studies.

A preliminary in-vivo study was performed on a new modified release system which contained diltiazem hydrochloride. The system consisted of swellable minimatrices that were coated with an acrylic polymeric film. The film thickness, because of its pH-dependent solubility, might represent a critical variable with regard to in-vivo release. In order to evaluate the influence of such a variable on in-vivo behaviour, two minimatrices formulations with differing film thickness were tested versus a commercial tablet. The in-vivo study, which was based on a balanced incomplete block design, involved six volunteers in two sequences. The drug was quantified in plasma by an HPLC method. Computation and statistical analysis of pharmacokinetic parameters were performed by means of SIPHARR package (Simed, F). The results show that the approach of film coating, in order to modify the release rate from minimatrices, is feasible, but it must be improved; in particular the results point to the necessity of reducing the film susceptibility to pH changes.

Adult↗
PubMedDate not supplied

Rheological and mechanical properties of pharmaceutical gels. Part I: Non-medicated systems.

Non-medicated gel systems based on polymers of different chemical nature and source have been characterized for rheological as well as for gel strength properties: a synthetic product, polyacrylic acid and a natural product, scleroglucan, both known to produce true gels, and two semi-synthetic materials, sodium carboxymethylcellulose and hydroxypropylmethylcellulose, both known to originate polymeric colloidal solutions, have been chosen. In particular, the rheological analysis involved the comparison of the different polymers on the basis either of viscosity (constant rate test) or of viscoelastic measurements (oscillation test). Subsequently the possible relationships between either viscosity or viscoelastic parameters (G', G", tg delta) and the gel strength parameter have been investigated. The mechanical resistance of the pharmaceutical gels examined didn't depend on the viscosity but rather on the viscoelasticity of the systems. In particular, low tg delta values were always accompanied by high gel strength values. A rank order correlation was found between the tg delta values obtained for the various samples at different frequency values and the relevant gel strength parameter: this suggests that mechanical resistance measurements, similarly to viscoelastic ones, give information on the structural properties of the samples and therefore represent a suitable tool in the optimization of gel formulations.

Elasticity↗
PubMedDate not supplied

Rheological and mechanical properties of pharmaceutical gels. Part II: Medicated systems: relevance to hydration properties and drug release.

Aim of this work was to evaluate the influence of rheological and mechanical properties of medicated gels containing two viscosity grades of either sodium carboxymethylcellulose or polyacrylic acid on hydration properties and drug release. The two polymers were chosen since they produce different semi-solid systems: polymeric colloidal solutions in the case of sodium carboxymethylcellulose and true gels in the case of polyacrylic acid. Salicylic acid and sodium salicylate were used as model drugs for sodium carboxymethylcellulose solutions, benzoic acid and sodium benzoate were employed for polyacrylic acid gels. The relationship previously found (Part I of this study) between the viscoelastic (tg delta) and the gel strength parameters in non-medicated gelified vehicles also exists in medicated gels: the higher the tg delta, the lower the gel strength. The results obtained on isoviscous samples (either colloidal solutions or true gels), containing two viscosity grades of the same polymer, demonstrate that an increase in tg delta and the concomitant decrease in the mechanical resistance of the sample always accompany an improvement in hydration properties. The different rheo-mechanical and hydration properties entrain different release profiles only when drugs are suspended in the vehicle (i.e. in the case of the free acids here considered). In these cases, the limiting step for drug release is likely the preliminary drug dissolution, which is in turn affected by the hydration propensity of the vehicle.

Excipients↗
PubMedDate not supplied

Characterization of rheological and mucoadhesive properties of three grades of chitosan hydrochloride.

In the present study the rheological and mucoadhesive properties of three viscosity grades of a cationic polymer, chitosan, were investigated to assess the suitability of this polymer for gastroadhesive formulations. The influence of the pH, ionic strength and temperature of the hydration medium on the rheological properties was studied. The mucoadhesive performance was assessed in vitro by means of rheological synergism and tensile stress testing. A correlation was found between rheological synergism and tensile parameters (force of detachment and work of adhesion), which proves that both methods can correctly predict the mucoadhesive performance of the polymers examined. It was found that the interaction of chitosan with mucin decreases on increasing molecular weight.

Biopolymers↗