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Biomedical subjects

D Brooke

Publications and source records attributed to D Brooke.

At least 37 records · Page 2Linked to original sources
PubMed1985

Characterization of polymorphism of gepirone hydrochloride.

Gepirone hydrochloride, an investigational anxiolytic drug, was found to have at least three polymorphic forms which melted at 180 degrees C (I), 212 degrees C (II), and 200 degrees C (III). Thermal analytical studies showed that forms I and II were an enantiotropic pair, as were forms I and III. Form III was monotropic with form II and there was no temperature at which III was the most stable polymorph. Solubility data from powder dissolution studies were used to estimate a transition temperature of 74 degrees C for the enantiotropic pair of I and II. The difference in enthalpy was 4.5 kcal/mol at 74 degrees C and 2.54 kcal/mol at 25 degrees C. Form I was the most physically stable below 74 degrees C, whereas form II was the most stable above 74 degrees C. Essentially pure samples of I and II could be obtained easily, but pure III could be developed only transiently on the differential scanning calorimeter heating block. Video taping of hot-stage microscopic observations for review was helpful for detecting seed crystals of II or III in samples of I. The information developed is presented in a hypothetical free energy-temperature diagram.

Calorimetry, Differential Scanning↗
PubMed1979

High-performance liquid chromatographic analysis of cyclophosphamide.

A reversed-phase high-performance liquid chromatographic technique is described for the analysis of cyclophosphamide in the presence of its hydrolysis products. The drug was quantified using a UV detector at a low wavelength. A single band was observed for the intact drug, which was well separated from tis hydrolysis product(s). Quantificaiton was obtained with adequate precision by the use of an injector loop or a suitable internal standard (hydrocortisone). The technique requires no extraction of the drug from aqueous solution or derivatization for analysis. The method was applied to partially hydrolyzed and to known solutions of cyclophosphamide. With suitable modification, the method may be useful for analysis of dosage forms but probably lacks the sensitivity necessary for analysis of the drug in biological samples.

Chromatography, High Pressure Liquid↗
PubMed1977

Zero-order drug delivery system: theory and preliminary testing.

A new approach to zero-order drug delivery that includes geometric factors is described. An experimental device based on the theory was tested by following the release of stearic acid into ethanol. Three separate trials indicated that the solid was released via a zero-order process in a reproducible manner.

Delayed-Action Preparations↗
PubMed1977

Dissolution profile for multisized drug particles: new approximate expression.

New approximate expressions for the weight fraction undissolved were obtained using the Taylor series expansion. These approximations were tested using simulated data for multisized drug particle populations. The resulting calculations show that: (a) the approximations are not dependent on a knowledge of the analytical form of the particle-size density function, (b) the distribution effects are accounted for, but only a knowledge of the sample mean and standard deviation is required, and (c) the approximations (especially on a weight basis) lead to values within the limits of error in dissolution studies, thus posing the question of whether published exact experessions have practical value.

Chemistry, Pharmaceutical↗
PubMed1977

Anaemia treatment trials in a rural population of Tanzania.

In a coastal population in whom anaemia was common, two randomised controlled trials were undertaken to investigate the effectiveness of treating iron deficiency anaemia at a dispensary and at primary schools. For anaemic adult villagers treated at a dispensary, one dose of tetrachlorethylene for hookworm infection and a once per week visit to collect medicines were found to be satisfactory. A small but significant increase in haemoglobin level was produced by four weeks oral iron therapy, but this was only maintained after seven months by the group that had initially also received tetrachlorethylene. In children (5-14 years) no significant rise in haemoglobin level was obtained by using oral iron and/or TCE, either at the dispensary or at the primary schools. This suggests that malaria was a more potent cause of anaemia in these children.

Adolescent↗
PubMed1976

Application of trihydroxyindole reaction to methanesulfonanilides: fluorometric analysis for soterenol and mesuprine.

Methanesulfonanilides, like soterenol and mesuprine, which are bioisosteric with adrenergic catecholamines, form fluorescent species when subjected to the trihydroxyindole reaction. Presumably, the fluorescence is due to adrenolutin-like species formed from aminochrome intermediates. Fluorescence was not induced in a relative of soterenol where a methyl group was added to the sulfonamido nitrogen, a fact that suggests the presence of a quinoid intermediate in the reaction scheme of soterenol. A ring isomer of soterenol, where the methanesulfonamido and hydroxyl groups were interchanged, produced only about 5% as much fluorescence response as soterenol. The sterenol counterparts to isoproterenol and isoproterenol sulfonic acid did not produce fluorescence when treated like soterenol. This finding and the fact that response was linear with concentration for soterenol and mesuprine suggest that a fluorometric analysis could be developed for these methanesulfonanilides.

Anilides↗
PubMed1975

Sieve cuts as monodisperse powders in dissolution studies.

Dissolution profiles are calculated for sieve cuts of varying width based on a derived equation, which assumes diffusion rate-limited dissolution under sink conditions from spherical particles. It is shown that even the narrowest of sieve cuts may vary from cube root law expectations by as much as 3 percent, depending on the distribution of particles across the cut. Much smaller deviations from the cube root law occur when the weight distribution of diameters is constant across a sieve cut. It is concluded that when experimental data are treated on the assumption that sieve cuts act like monosized powders, errors generally will be acceptable except in cases of critical tests of dissolution rate theory. In those cases, more information about the powder distribution should be given.

Particle Size↗
PubMed1975

Effect of briefly heating cyclophosphamide solutions.

Solutions containing cyclophosphamide monohydrate were heated to 50 C, 60 C, 70 C and 80 C for 15 minutes and then assayed for potency. Solutions heated to 50 Cor 60 C did not change appreciably; those heated to 70 C and 80 C assayed at 90.2% and 77.5%, respectively, of initial potency. The values compared well with those calculated using the Arrhenius equation. It is concluded that warming vials of cyclophosphamide monohydrate after adding an aqueous vehicle (in order to achieve rapid dissolution) could decrease the potency of the final injectable product.

Cyclophosphamide↗