PubMed Health⌕ Search

Biomedical subjects

A W Newman

Publications and source records attributed to A W Newman.

6 recordsLinked to original sources
PubMed2001

Chemical reactivity in solid-state pharmaceuticals: formulation implications.

Solid-state reactions that occur in drug substances and formulations include solid-state phase transformations, dehydration/desolvation, and chemical reactions. Chemical reactivity is the focus of this chapter. Of particular interest are cases where the drug-substance may be unstable or react with excipients in the formulation. Water absorption can enhance molecular mobility of solids and lead to solid-state reactivity. Mobility can be measured using various methods including glass transition (T(g)) measurements, solid-state NMR, and X-ray crystallography. Solid-state reactions of drug substances can include oxidation, cyclization, hydrolysis, and deamidation. Oxidation studies of vitamin A, peptides (DL-Ala-DL-Met, N-formyl-Met-Leu-Phe methyl ester, and Met-enkaphalin acetate salt), and steroids (hydrocortisone and prednisolone derivatives) are discussed. Cyclization reactions of crystalline and amorphous angiotensin-converting enzyme (ACE) inhibitors (spirapril hydrochloride, quinapril hydrochloride, and moexipril) are presented which investigate mobility and chemical reactivity. Examples of drug-excipient interactions, such as transacylation, the Maillard browning reaction, and acid base reactions are discussed for a variety of compounds including aspirin, fluoxitine, and ibuprofen. Once solid-state reactions are understood in a pharmaceutical system, the necessary steps can be taken to prevent reactivity and improve the stability of drug substances and products.

Chemistry, Pharmaceutical↗
PubMed1999

Constitutional rights and hypnotically elicited testimony.

Despite the former popularity of hypnosis as a way of "improving" eyewitness memory, many courts almost always regard the use of this testimony to be inadmissible, whereas others allow it only when strict procedural guidelines have been followed. Although the U.S. Supreme Court recognized a defendant's constitutional right to admit his own hypnotically elicited testimony, others have recognized a constitutional basis to exclude hypnotically elicited testimony in most other circumstances.

Civil Rights↗
PubMed1996

Quantitation of cefepime.2HCl dihydrate in cefepime.2HCl monohydrate by diffuse reflectance IR and powder X-ray diffraction techniques.

The identification, characterization and quantitation of crystal forms is becoming increasingly important within the pharmaceutical industry. Multi-disciplinary, physical analytical techniques are necessary for this task. In this work, diffuse reflectance mid-infrared (IR) and powder X-ray diffraction (XRD) analyses were used to identify two different hydrated forms of cefepime.2HCl, a cephalosporin. Characterization of the mono- and dihydrate forms led to separate IR and XRD quantitative assays for the determination of dihydrate content in cefepime.2HCl monohydrate bulk material. For the IR assay, a working range of 1.0-8% (w/w) was established with a minimum quantifiable level (MQL) of 1.0% (w/w) and a limit of detection (LD) of 0.3% (w/w) dihydrate in monohydrate material. The XRD assay displayed a working range of 2.5-15% (w/w) with an MQL of 2.5% (w/w) and an LD of 0.75% (w/w). Cross validation was performed between the two techniques, with a good correlation displayed for each assay as compared with the known concentrations and as compared with each other. In addition, a full evaluation of potential assay errors was made.

Cefepime↗
PubMed1993

Changes in material properties accompanying the national formulary (NF) identity test for microcrystalline cellulose.

It has been found that the current NF identity test for microcrystalline cellulose is actually an assay of the response of the material to energy dissipation expended during the analysis procedure. The blending step needed to effect suspension of the material results in a disintegration of the microcrystalline particles and a concomitant increase in the viscosity of the slurry viscosity. These effects were shown not to be unique functions of either blender speed or blending time. The passage or failure of a given sample of microcrystalline cellulose under the conditions of the identity test was found to be a consequence of the test conditions used. Any given sample of microcrystalline cellulose can be made to pass the identity test if it is blended for a sufficiently long time or at a sufficiently high speed. The test is sufficient, however, to differentiate powdered cellulose from powdered cellulose.

Cellulose↗
PubMed1991

Physical characterization of pharmaceutical solids.

A general review of the methods available for the physical characterization of pharmaceutical solids is presented. The techniques are classified as being on the molecular level (properties capable of being detected in an ensemble of individual molecules), the particulate level (properties which can be detected through the analysis of an ensemble of particles), and the bulk level (properties which can be measured only using a relatively large amount of material). The molecular-level properties discussed are infrared spectroscopy and nuclear magnetic resonance spectrometry, the particulate-level properties discussed are particle morphology, particle size distribution, powder X-ray diffraction, and thermal methods of analysis, and the bulk-level properties discussed are surface area, porosity and pore size distribution, and powder flow characteristics. Full physical characterization of three modifications of lactose (hydrous, anhydrous, and Fast-Flo) is presented to illustrate the type of information which can be obtained using each of the techniques discussed.

Magnetic Resonance Spectroscopy↗