Biomedical subjects

G Bramanti

Publications and source records attributed to G Bramanti.

At least 19 recordsLinked to original sources

PubMed2002

Scaling breakdown: a signature of aging.

We prove that the Lévy walk is characterized by bilinear scaling. This effect mirrors the existence of a form of aging that does not require the adoption of nonstationary conditions.

Journal Article↗

PubMed2000

Evaluation of transcutol as a clonazepam transdermal permeation enhancer from hydrophilic gel formulations.

The influence of diethyleneglycol monoethyl ether (transcutol), alone or in combination with propylene glycol, on clonazepam permeation through an artificial membrane and excised rabbit ear skin from Carbopol hydrogels was investigated. Drug kinetic permeation parameters were determined for both series of experiments and compared. Rheological characteristics, drug solubility and membrane/vehicle partition coefficient for each gel formulation were also determined, and their role in the formulation performance was investigated. Both series of experiments showed an increase of drug permeation as a function of transcutol content in the formulation. The combination of transcutol and propylene glycol resulted in a synergistic enhancement of clonazepam flux. A different trend was found in experiments with gels containing mixtures of the two enhancers, where an increase (in the case of artificial membrane) or a decrease (in the case of rabbit ear skin) of drug permeation was found by increasing the transcutol/propylene glycol ratio in the mixture. Such a result is explained on the basis of the particular mechanism of action demonstrated for transcutol which associates the increase of drug solubility to the potent effect of a depot in the skin.

Administration, Cutaneous↗

PubMed1999

Influence of the preparation method on the physicochemical properties of binary systems of econazole with cyclodextrins.

Equimolar combinations of econazole, a very poorly water soluble antifungal agent, with beta-cyclodextrin and statistically substituted methyl-beta-cyclodextrin were investigated for both solid state characterization (differential scanning calorimetry, hot-stage microscopy, infrared spectroscopy, scanning electron microscopy) and dissolution properties (dispersed amount method). The influence of the preparation method (physical mixing, ball-milling, kneading, sealed-heating) on the physicochemical properties of the products was evaluated. Kneading and sealed-heating techniques led to amorphous products in the case of systems with methyl-beta-cyclodextrin, whereas crystalline drug was still clearly detectable in all products with beta-cyclodextrin. Independently of the preparation technique, all combinations with methyl-beta-cyclodextrin yielded better performance than the corresponding ones with beta-cyclodextrin. However, the influence of the preparation method was clearly more marked for products with methyl-beta-cyclodextrin and made to be possible to better display the different performance of the examined carriers. In fact, the sealed-heated with the beta-derivative showed an increase of drug dissolution efficiency of 130% with respect to the corresponding physical mixture, in comparison to the 70% increase obtained from that with beta-cyclodextrin. Moreover, whereas the difference in dissolution efficiency values between coground products was only about 8% in favor of the beta-derivative, it reached 80 and 90% between sealed-heated and kneaded products, respectively.

Antifungal Agents↗

PubMed1999

Thermal behavior and dissolution properties of naproxen from binary and ternary solid dispersions.

Solid dispersions of 10% w/w naproxen (NAP) in poly(ethylene glycol) (PEG) (4000, 6000, or 20,000) as a carrier with or without incorporation of anionic (sodium dodecyl sulfate; SDS) or nonionic (Tween 80; Tw80) surfactant were prepared by the melting method. Physicochemical characteristics were determined by differential scanning calorimetry (DSC) and X-ray diffraction analysis. The results of dissolution studies showed that drug dissolution properties were better from ternary systems than from binary systems since in the former the wetting and solubilizing effects of surfactant and polymer were additive. No influence of the PEG molecular weight was found. The best performance given by anionic surfactant has been attributed to several factors, such as higher hydrophilicity, better solubilizing power, and most facile interaction with both drug and PEG. No important changes in solid-state characteristics or in drug dissolution properties were found after 30 months storage for dispersions with or without surfactant. Only a slight decrease in initial drug dissolution rate was observed at the highest concentration (10% w/w) of SDS.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1998

Compatibility study between ibuproxam and pharmaceutical excipients using differential scanning calorimetry, hot-stage microscopy and scanning electron microscopy.

Differential scanning calorimetry (DSC) was used as a screening technique for assessing the compatibility of ibuproxam with some currently employed pharmaceutical excipients. The influence of processing effects (simple blending, cogrinding or kneading) on drug stability was also evaluated. On the basis of DSC results, ibuproxam was found to be compatible with corn starch, avicel and sodium carboxymethylcellulose. Some drug-excipient interaction was observed with polyethyleneglycol 4000, palmitic acid, stearic acid, Ca and Mg stearate. Actual solid-phase interactions of the drug with polyvinylpolypyrrolidone and polyvinylpirrolidone K30 were induced by mechanical treatments. Hot-stage microscopy (HSM) and scanning electron microscopy (SEM) were of help in interpreting the DSC results and excluding in all cases relevant pharmaceutical incompatibilities.

Benzeneacetamides↗

PubMed1993

1,2-Cyclomethylenecarboxylic monoamide hydroxamic derivatives. A novel class of non-amino acid angiotensin converting enzyme inhibitors.

A series of monoamidic derivatives of cis- and trans-1,2-cyclohexanedicarboxylic and 1,2-cyclopentanedicarboxylic acids bearing either a carboxylic, sulfhydrylic, or hydroxamic group in the side chain were synthesized and evaluated in vitro for their inhibitory activity against angiotensin converting enzyme. The compounds were designed as potential ACE inhibitors of novel structure, assuming that a monoamidic residue of an 1,2-cyclomethylenedicarboxylic acid could be an alternative structure to the acylproline moiety, the carboxyl-terminal portion common to various ACE inhibitors. The most active compounds were found in the hydroxamic derivatives of cyclohexane series; within this series of derivatives a marked increase of potency was caused by alkylation of the amidic nitrogen with a methyl or ethyl group. Therefore enantiomers of the selected hydroxamic derivatives of cis- and trans-1,2-cyclohexanedicarboxylic acid were prepared by two different chiral synthetic routes and evaluated in vitro for their ACE inhibitor potencies. The active enantiomers both of the cis series (21a, 21c) and trans series (16b, 16d) were found to have all R configuration at the C-2 and R or S configuration at the C-1, while in the classical ACE inhibitors S configuration at the terminal carboxylate (corresponding to the C-1 of our compounds) is strictly required for activity. The most potent compound of the series was (1S,2R)-cis-2[[[2-(hydroxyamino)-2-oxoethyl]methylamino]carbonyl] cyclohexanecarboxylic acid (21a) with an IC50 value of 7.0 nM compared with the value of 3.0 nM for captopril. Further 21a was shown to be highly selective and competitive ACE inhibitor. These results indicate that this non-amino acid structure of inhibitors meets the ACE active site requirements for the binding. The binding compatibility of the most active compounds with a model of ACE active site was evaluated by molecular modeling techniques.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1992

Improvement of clonazepam release from a Carbopol hydrogel.

The performance of Tween 80, Tween 60, oleic acid, oleyl alcohol and Azone as enhancers of clonazepam permeation from a Carbopol hydrogel through a cellulose nitrate membrane was investigated. The effect of incorporating methyl beta-cyclodextrin (DS 1.8) in combination with clonazepam as a solid phase into some vehicles was also tested. In vitro release studies were carried out with a Sartorius apparatus and the following parameters were evaluated: drug solubility in the vehicle; partition coefficient of the drug between lauryl alcohol (the solvent which impregnates the membrane) and the vehicle; steady state flux; permeability constant; diffusion coefficient; lag time. The release kinetics followed a nearly zero-order pattern, although the diffusion-controlled mechanism might also have been operative. Maximum drug release (2.5 times that of the gel base) was achieved for the formulation containing clonazepam and methyl beta-cyclodextrin in a 1:1 (mol/mol) ratio as a solid phase, in a vehicle composed of water, propylene glycol, Tween 80 and Azone at a mass fraction of 43%, 50%, 2% and 5%, respectively.

Acrylic Resins↗

PubMed1990

In vitro study of clonazepam diffusion kinetics from solutions or hydrophilic gel.

Preliminary studies were conducted to evaluate the influence of temperature, pH and ionic strength of the donor and receptor medium on the solubility, partition coefficient and diffusion rate of clonazepam across a lipophilic artificial membrane, in view of future setting up of transdermal formulation of this drug. The in vitro release of clonazepam from a carbopol hydrogel was also investigated.

Chemical Phenomena↗

PubMed1989

Formulation factors influencing the release of clonazepam from a carbopol hydrogel.

A study of formulation factors influencing the release of clonazepam from a Carbopol hydrogel through a cellulose nitrate membrane impregnated with lauryl alcohol was performed using two diffusion cell assemblies. The formulation variables were the cosolvent effects of propylene glycol and polyethylene glycol of different molecular weights in aqueous solutions of various composition. The gel formulation phenomenologically behaves as a zero-order release system, although the diffusion controlled mechanism may also be operative. The results showed that both methods were practically equivalent in terms of drug release profile and total drug released allowing the best formulation to be found.

Acrylic Resins↗

PubMed1988