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Biomedical subjects

D R Flanagan

Publications and source records attributed to D R Flanagan.

29 records · Page 2Linked to original sources
PubMed1990

Degradation of poly(ester) microspheres.

Biodegradable polymeric microspheres have been prepared by spray drying, precipitation, rotary evaporation and press grinding methods. Erosion of microspheres of poly(lactide), poly(3-hydroxybutyrate), copolymers of lactide and glycolide, and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate at 85 degrees C and 37 degrees C have been studied using ion chromatography, nuclear magnetic resonance, residual mass measurements, viscometry and gel permeation chromatography. Such studies demonstrated that these polyester matrices degraded via (1) random chain scission and (2) release of soluble monomeric and oligomeric products. Protein release from microspheres prepared by these methods indicated that most of the protein is released before the polymer matrix loses weight.

Biodegradation, Environmental↗
PubMed1989

Micellar solubilization of a new antimalarial drug, beta-arteether.

beta-Arteether (1) is a new antimalarial drug derived from artemisinin (2, quinghaosu). Compound 1 is quite water insoluble, but very soluble in a variety of organic solvents. Solubilization in a variety of surfactants was investigated to obtain higher concentrations of 1 in aqueous solutions. Anionic and cationic surfactants exhibited dramatic solubilizing ability for 1, while nonionic surfactants showed significantly lower solubilizing ability. The solubilization data are analyzed on the basis of a pseudo-phase model with 1 exhibiting a high partition coefficient into the micellar phase. An empirical model is presented to identify the possible sites of solubilization of 1 in the micelle.

Antimalarials↗
PubMed1986

Determination of the dissolution rate controlling process for isomeric amides in alkane solvents.

The mechanisms that control the dissolution rates of chemical compounds in liquids have long been of interest to pharmaceutical scientists. Generally, control of the dissolution rate can be classified as being by interfacial reaction rate or by the rate of mass transport. Little work has been done in the area of sparingly soluble compounds dissolving in nonpolar organic solvents. In this study the dissolution of three isomers of methylacetanilide was investigated in three nonpolar organic solvents (hexane, heptane, and cyclohexane). The dissolution apparatus used a flat plate into which the nondisintegrating tablet could be placed so that dissolution occurred only from one face of the tablet. Agitation was provided by a four-bladed stirrer whose outer edge was 2 cm from the tablet surface. Dissolution data were collected only for concentrations less than 5% of the saturation solubility of the given compound in the given solvent. All dissolution profiles were linear. Dissolution rates were obtained from the slopes of these plots. Plots of In (dissolution rate) versus In (stirring speed) were also linear and yielded slopes that were close to the value of 0.50 predicted by the convective diffusion model employed.

Amides↗
PubMed1978

Evaluation of an oral prolonged-release antibiotic formulation.

The antibiotic cephalexin was formulated as an oral prolonged-release tablet and evaluated by in vitro dissolution testing as well as in vivo in 10 human subjects. Comparisons were made of the time course of the blood levels among the prolonged-release formulation, the commercially available capsule, and intravenous administration. Even though lower peak blood levels were attained in the prolonged-release tablet, absorption continued for at least 6 hr. Comparison with in vitro dissolution data showed that absorption was dissolution rate limited. Bioavailability comparisons showed that the prolonged-release formulation was completely available, as was the commercial oral capsule.

Administration, Oral↗
PubMed1977

Rapid sensitive fluorometric analysis of cephalosporin antibiotics.

A rapid and sensitive fluorometric analysis for cephalosporins, which can also be applied to penicillins, is presented. The method involves reaction with 0.1 N sodium hydroxide at 100 degrees, producing stable fluorescent products. This method was applied to cephalexin and ampicillin with detection at concentrations as low as 0.01 mug/ml.

Ampicillin↗
PubMed1977

Convective diffusional analysis for drug transport through a tubular polymeric membrane.

The transport of three p-aminobenzoate esters (ethyl, butyl, and hexyl) through a tubular dimethyl polysiloxane membrane into a flowing liquid was investigated. The tubular configuration permits the exact determination of the convective diffusional contribution to membrane transport with models that account for fluid hydrodynamics. The observed transport behavior ranged from complete convective diffusion control for the hexyl ester to complete membrane control for the ethyl ester; the butyl ester exhibited a change in control with flow rate. The implications of convective diffusional considerations to intestinal absorption and dissolution studies are discussed.

4-Aminobenzoic Acid↗