[The optic pattern of erythro-3,4-dihydroxynorephedrines].
Explore the source record for details and available documents.
Catecholamines↗
Biomedical subjects
U Conte
Publications and source records attributed to U Conte.
[Synthesis and configuration of DL-threo-3,4-dihydroxynorephedrine].
Explore the source record for details and available documents.
Chemistry, Pharmaceutical↗
Influence of route of administration and dosage form in the pharmacokinetics and bioavailability of salbutamol.
The present study was carried out to define the pharmacokinetics of salbutamol sulfate administered to mongrel dogs in five pharmaceutical forms via two routes of administration. One pharmaceutical form was administered intravenously (Ventolin i.v.) while the other four were administered orally (Ventolin: immediate-release formulation, Volmax: commercial osmotic pump, SG7 and SG14: sustained-release hydrophilic matrices developed in our laboratory). We obtained a first-order release kinetic of the salbutamol from Ventolin and SG7, whereas a zero-order release kinetic was observed for SG14 and Volmax formulations. Oral bioavailability was 80% and there were neither significant differences (P > 0.05) in terms of the calculation method used (relation of the areas under the plasma level curve Loo-Riegelman, deconvolution) nor in terms of the dosage form (Ventolin Volmax, SG7 and SG14). The elimination half-life value of salbutamol was 1.2 h when administered intravenously; this parameter had a value of 3.0 h for the immediate-release formulation and ranged between 5.4 and 7.2 h in the sustained-release formulations when administered orally. These changes in the half-life value of the sustained-release formulations will allow us to modify the frequency of administration in relation to immediate-release formulations.
Administration, Oral↗
Preparation and characterization of ampicillin loaded methylpyrrolidinone chitosan and chitosan microspheres.
Ampicillin was embedded in microparticles made of a new derivative of chitosan: methylpyrrolidinone chitosan. They were prepared using different drug-to-polymer weight ratios and by a spray-drying technique. Spray-dried drug-loaded chitosan microspheres were prepared for comparison. The microparticles were characterized by scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry (DSC) and in vitro drug release. Microbiological assay was performed using different bacterial strains. Spray-dried microspheres of almost spherical shape, smooth surface and narrow size distribution were always obtained. Ampicillin loaded into both polymer matrices showed amorphous behaviour as determined by DSC. Drug-loaded microspheres resulted to control the drug release in a 30-120 min range, depending on chitosan type. Thermal denaturation of the microspheres does not modify drug release rate. The results of the microbiological assay show that the loading of ampicillin into chitosans is able to maintain or improve the anti-bacterial activity of the drug.
Ampicillin↗
A calorimetric study on diflunisal release from poly(lactide-co-glycolide) microspheres by monitoring the drug effect on dipalmitoylphosphatidylcholine liposomes: temperature and drug loading influence.
Diflunisal release from poly-Lactide-co-Glycolide (50:50, 34,000 MW) microspheres loaded with two different amounts of drug (2.5 +/- 0.5% and 10 +/- 0.5% w/w) was monitored by following the effects exerted by the drug on the thermotropic behavior of dipalmitoylphosphatidylcholine unilamellar vesicles at different temperatures. The effects of the drug released from the microspheres on the thermotropic behavior of lipid aqueous dispersion containing different molar ratios of drug was detected by differential scanning calorimetry and was compared with the effects exerted by the free Diflunisal. Diflunisal affects mainly the temperature (Tm) of the transition characteristic of phospholipid vesicles as model biomembrane, causing a shift toward lower values. This shift was modulated by the drug molar fraction with respect to the lipid concentration in the aqueous dispersion. Afterward, calorimetric measurements were performed on suspensions of blank liposomes added to weighed amounts of unloaded and differently Diflunisal-loaded microspheres as well as free powdered Diflunisal after incubation for increasing times at three different temperatures (25, 37, and 50 degrees C). The Tm shifts of the lipid bilayer, caused by the drug released from polymeric system as well as by the free drug during incubation periods, were compared with that caused by free drug increasing molar fractions dispersed directly on the membrane, employed as a calibration curve to obtain the fraction of drug released. This in vitro study suggests that the kinetic process involved in drug release is influenced by the amount of drug loaded in the microspheres as well as by the temperature acting on drug solubility and membrane disorder. This drug release model, monitored by the calorimetric technique shows that a) the poly-Lactide-co-Glycolide microspheres are a good delivery system able to sustain the drug release; b) the differential scanning calorimetry technique applied on the drug interaction with biomembranes constitutes a good tool to follow the drug release; 3) this model, representing an innovative alternative in vitro model, should be used to determine the different kinetics involved in the drug transfer from a drug delivery system to a membrane as uptake site.
1,2-Dipalmitoylphosphatidylcholine↗
Cellulose acetate butyrate and polycaprolactone for ketoprofen spray-dried microsphere preparation.
Ketoprofen-loaded microspheres made with a polymeric blend were prepared by a spray-drying technique. Organic solutions of two polymers, cellulose acetate butyrate (CAB) and poly(epsilon-caprolactone) (PCL), in different weight ratios, and of ketoprofen (Ket) were prepared and sprayed, in different experimental conditions, achieving drug-loaded microspheres. The obtained spray-dried microspheres were characterized in terms of yield of production, shape, size, surface properties and drug content, and their in vitro drug release behaviours were determined at different pH values.
Cellulose↗
Spray-dried albumin microspheres for the intra-articular delivery of dexamethasone.
This work deals with the preparation of corticosteroid-loaded albumin microspheres designed for intra-articular administration. Dexamethasone was chosen as the model drug and bovine serum albumin was used as the biodegradable, natural polymer. Albumin microspheres were produced by spray drying, a 'one-step' technique seldom used in the preparation of microparticulate drug delivery systems with particle sizes < 10 microns. The effects of both polymer/drug ratio used in the formulations and the different heat-stabilization conditions were evaluated on morphology, size, solubility characteristics, drug loading and 'in vitro' drug release of the microparticles.
Dexamethasone↗
Cellulose acetate trimellitate ethylcellulose blends for non-steroidal anti-inflammatory drug (NSAID) microspheres.
Ketoprofen (Ket), a non-steroidal anti-inflammatory drug, has been incorporated into polymeric micromatrices (microspheres) prepared by a spray drying process and made of cellulose acetate trimellitate (CAT)/ethylcellulose (EC) blends. Drug loaded microspheres were obtained by spray-drying organic solutions of the two polymers and the drug. Characterization of the microparticles (morphology, particle size distribution, drug content, yield of production, surface properties, solvent residues) was carried out and in-vitro release behaviour measured. The release rate of the drug diminished as the proportion of EC was raised.
Anti-Inflammatory Agents, Non-Steroidal↗
PDLLA microspheres containing steroids: spray-drying, o/w and w/o/w emulsifications as preparation methods.
Hydrocortisone and its more soluble ester, hydrocortisone 21-acetate, have been incorporated into poly(D,L-lactic) acid (PDLLA) microspheres using single, double emulsion/solvent evaporation and by spray-drying techniques. This paper describes the characterization of the microparticles obtained (morphology, particle size distribution, drug content, yield of production, in vitro drug release behaviour) and a comparison of the results (drug loading, drug release, size of the microspheres) obtained from the different techniques used. These results demonstrate that by using a relatively more soluble ester of an insoluble steroid, hydrocortisone, the drug content within the microspheres can be increased, together with a high efficiency of loading, irrespective of the technique employed. In the case of hydrocortisone, spray-drying produces the highest loading and encapsulation efficiency compared to both single and double emulsion methods for microspheres of similar size (about 2-4 microns) and suitable for lung delivery, but with lower yields (about 55% versus about 33%).
Calorimetry, Differential Scanning↗
Cross-linked sodium carboxymethylcellulose as a carrier for dissolution rate improvement of drugs.
The dissolution rate is often the limiting step in gastrointestinal absorption of water insoluble drugs from solid oral dosage forms. The aim of this work was to use a swellable polymer chosen among superdisintegrants, for improving the dissolution rate of a sparingly soluble drug, loaded on its surface. Nifedipine, which has a very low water solubility, was chosen as a model drug, while cross-linked sodium carboxymethylcellulose (Ac-Di-Sol) was chosen as the swellable polymer. The Nifedipine/Ac-Di-Sol systems were prepared using two different techniques: evaporation and spraying; in some preparations polyethylene glycol (PEG 1500), or sucrose palmitate (Sucrodet), or dioctyl sodium sulfosuccinate (Aerosol OT) were added. The results of the dissolution tests showed that the dissolution rate of Nifedipine from the systems prepared increases, particularly in the case of the preparation composed of Ac-Di-Sol plus surfactant agents.
Carboxymethylcellulose Sodium↗