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Biomedical subjects

J Dressman

Publications and source records attributed to J Dressman.

8 recordsLinked to original sources
PubMed2001

Batch-to-batch reproducibility of St. John's wort preparations.

Over the last few years, St. John's Wort products have enjoyed a tremendous surge in interest and sales for the therapy of mild to moderate depression. Although the complete spectrum of active substances in this herbal extract has not yet been elucidated, it is certain that hyperforin is an important component. Further, it appears that the hypericins may also contribute to the antidepressive activity. In this study, the content uniformity of eleven St. John's Wort products sold exclusively in pharmacies was determined. The main objective was to determine the batch-to-batch reproducibility of the various products. The hyperforin was analysed according to a previously published HPLC method, while the total hypericin content was determined by an electrochemical method. The results indicate that some, but not all, products show very reproducible batch-to-batch properties. Also, individual products have different hypericin and hyperforin levels, and are therefore not switchable--even when products are manufactured under similar extraction and processing conditions, have the same raw material:extract ratios (on a dry basis) and contain the same amount of extract per unit dosage form.

Anthracenes↗
PubMed2000

Improving drug solubility for oral delivery using solid dispersions.

The solubility behaviour of drugs remains one of the most challenging aspects in formulation development. With the advent of combinatorial chemistry and high throughput screening, the number of poorly water soluble compounds has dramatically increased. Although solid solutions have tremendous potential for improving drug solubility, 40 years of research have resulted in only a few marketed products using this approach. With the introduction of new manufacturing technologies such as hot melt extrusion, it should be possible to overcome problems in scale-up and for this reason solid solutions are enjoying a renaissance. This article begins with an overview of the historical background and definitions of the various systems including eutectic mixtures, solid dispersions and solid solutions. The remainder of the article is devoted to the production, the different carriers and the methods used for the characterization of solid dispersions.

Biological Availability↗
PubMed1988

Human postprandial gastric emptying of 1-3-millimeter spheres.

Microspheres of pancreatin should empty from the stomachs of patients with pancreatic insufficiency as fast as food. The present study was undertaken in 26 healthy subjects to identify the size of spheres that would empty from the stomach with food and to determine whether different meals alter this size. Spheres of predefined sizes were labeled with 113mIn or 99mTc. Using a gamma-camera, we studied the concurrent gastric emptying of spheres labeled with 113mIn and of chicken liver labeled with 99mTc in 100-g, 154-kcal or 420-g, 919-kcal meals, or the concurrent emptying of 1-mm vs. larger spheres. One-millimeter spheres emptied consistently (p less than 0.01, paired t-test) faster than 2.4- or 3.2-mm spheres when ingested together with either the 420- or 100-g meals. Thus, in the 1-3-mm range of diameters, sphere size was a more important determinant of sphere emptying than meal size. Statistical analyses indicated that spheres 1.4 +/- 0.3 mm in diameter with a density of 1 empty at the same rate as 99mTc-liver. Our data indicate some commercially marketed microspheres of pancreatin will empty too slowly to be effective in digestion of food.

Adult↗
PubMed1986

Effects of viscosity and fluid outflow on postcibal gastric emptying of solids.

It is known that the food-filled stomach retains large spheres or pieces of food, allowing the passage of food particles or of plastic spheres with diameters mainly below 2 mm. We have recently shown that spheres having densities greater or less than water emptied from the food-filled canine stomach more slowly than spheres of the same diameter with a density of 1. Thus, hydrodynamics seem to govern gastric emptying of spheres. The present studies were undertaken to determine how altering other hydrodynamic factors, viscosity and velocity of fluid outflow, might affect gastric sieving. Ten mongrel dogs were prepared with chronic duodenal fistulas, which allowed collecting and measuring of emptied spheres and food. The dogs were fed a standard meal of 75 g of steak plus 25 g of 99mTc-labeled chicken liver. Immediately afterward, 50 3.2-mm Teflon spheres were instilled into the stomachs along with 200- or 800-ml volumes of saline or saline plus guar (a viscous polysaccharide). Whether 200- or 800-ml volumes were instilled, the guar significantly sped the emptying of the spheres. Fluid outflow was twice as fast after the 800-ml instillates, but the faster outflow with the 800 ml of saline did not speed emptying of spheres. With the guar instillates, the faster outflow slightly sped the emptying of the spheres and significantly increased the diameter of emptied particles of 99mTc-labeled chicken liver. We conclude that meal viscosity significantly affects gastric sieving.

Animals↗
PubMed1985

Effect of size and density on canine gastric emptying of nondigestible solids.

Previous studies suggested that the food-containing canine stomach retains large, nondigestible spheres until all food has emptied; but it is not known whether there is a threshold size or a gradation of sizes that will empty along with food. Further, nothing is known of the effects of such parameters as density, shape, and surface energy on the emptying of nondigestible particles of any given size. To answer these questions 6 dogs with chronic duodenal fistulas were studied. Radiolabeled food and spheres were collected from the fistulas to compare the rate of gastric emptying of the spheres with that of the food. After a standard test meal of 99mTc-labeled liver, steak, and water, diverted chyme was collected over a stack of sieves in 30-min fractions over 5 postcibal hours. The percent of fed spheres and fed 99mTc-labeled liver in each collection was counted, and liquid chyme was returned to the distal duodenum. Spheres with a density of 1 emptied progressively faster as sphere diameters were decreased from 5 to 1 mm; but 0.015-mm spheres emptied at about the same rate as those with diameters of 1 mm. Emptying of the spheres became similar to emptying of the 99mTc-labeled liver at about 1.6 mm. Spheres with densities less than 1 or greater than 1 emptied more slowly than spheres of the same size with a density of 1, whereas paper squares emptied the same way as spheres of comparable size and density. Surface energy did not affect emptying. The findings indicated that both sphere size and density affect their emptying in the presence of food.

Animals↗
PubMedDate not supplied

Comparison of German St. John's wort products according to hyperforin and total hypericin content.

OBJECTIVES: To compare the hyperforin and hypericin content of currently available St. John's wort products and to determine their batch-to-batch reproducibility. DESIGN: Representative products were obtained either directly from the manufacturer or purchased from pharmacies in and around Frankfurt, Germany. For five batches from each of the eight manufacturers, 10 individual dosage forms (tablets or capsules) were analyzed for both hyperforin and hypericin content. SETTING: Laboratories of the Institute of Pharmaceutical Chemistry at Johann Wolfgang Goethe University, Frankfurt, Germany. PRODUCTS: Eight German St. John's wort products containing from 250 mg to 612 mg dry extract were studied. Three of these products are capsules, four are film-coated tablets, and one is a sugar-coated tablet. Two of the products (Jarsin 300 and Neuroplant 300) are also available in the United States. METHODS: Hyperforin concentrations were analyzed by high-performance liquid chromatography. Total hypericin concentrations were determined by polarography, an electrochemical method. Concentrations were compared among different batches of the same product and among products from different manufacturers. RESULTS: The products contained widely differing amounts of hypericin and hyperforin, even after correcting for differences in the amount of extract per dose. Some products demonstrated consistent concentrations of hyperforin and hypericin from batch to batch, others exhibited pronounced interbatch variability. CONCLUSION: The St. John's wort preparations studied exhibited large differences in hypericin and hyperforin content and are not interchangeable for the treatment of mild-to-moderate depression. Pharmacists should take this variability into account when counseling patients on the use of St. John's wort products.

Anti-Bacterial Agents↗