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J T Carstensen

Publications and source records attributed to J T Carstensen.

At least 19 recordsLinked to original sources
PubMed1992

Statistical approaches to stability protocol design.

In stability protocols, data are usually visualized as being generated, and stability evaluation is accomplished at a point in time when sufficient data have been accumulated. Often, data are simply treated by the "statistically best fit" and, as a consequence, statements describing some batches as being first order and some being zero order are frequently used. From a scientific point of view, it is more advantageous at the preformulation stage to ascertain what the stability profile should be (i.e., what the mechanism is) and then apply the statistics to this format. Examples are given of pH profiles, Arrhenius plotting, and dissolution data. In the first case, the use of fractional factorials (a matrix approach) is suggested.

Chemical Phenomena↗
PubMed1991

Methods for the assessment of the stability of tablet disintegrants.

To allow assessment of the long-term stability of tablet disintegrants, two mechanisms for their functionality (i.e., water uptake and swelling force generation) were monitored. Three disintegrants, alginic acid, sodium starch glycolate, and crospovidone, were used to establish the methodology. The water uptake and swelling force methodologies developed were reproducible, thus allowing for the evaluation of the effect of time, temperature, and humidity on these properties of disintegrants. The data obtained suggest that the process of water uptake and swelling force generation was essentially a two-step process. Initially, water entered the pore space in the powder bed; there was a definitive lag time before a swelling force was generated. In the stability evaluation of alginic acid and sodium starch glycolate, samples were stored for 1-year. Above 30 degrees C and 75% relative humidity, the swelling force performance of alginic acid was markedly affected. Changes seen with sodium starch glycolate were much less marked.

Alginates↗
PubMed1990

Amorphous-to-crystalline transformation of sucrose.

The transformation of amorphous sugar in the form of lyophilized spheres into crystalline sucrose was studied. The lyophilisate, when exposed to moist atmospheres, picks up moisture to a constant weight. The amount of moisture addition is a function of relative humidity of the atmosphere and temperature. The loose "lyophilisate structure" collapses to form a denser amorphous phase ("hydrated amorphate"). After a lag time which varies with relative humidity of the atmosphere and temperature, the hydrated amorphate loses moisture (weight) and, in the process, forms crystalline sucrose. The phase nature of the hydrated amorphate is equivalent to an aqueous solution that is supersaturated with respect to crystalline sucrose. A model was developed for the lag time which accounts for the experimental results.

Anhydrides↗
PubMed1979

Light stability of norethindrone and ethinyl estradiol formulation with FD&C colorants.

In general, light-sensitive tablets exhibit discoloration in the surface layer(s) only. A case is discussed where a quantitative interaction between a drug, ethinyl estradiol (in a combination tablet containing norethindrone and ethinyl estradiol), and a dye (FD&C Red No. 3) occurs, and discoloration exists throughout the tablet. The data suggest that accelerated light studies should be carried further than those dictated by predictive periods so that equilibrium levels can be deduced.

Coloring Agents↗
PubMed1979

Dielectric constants of solid-liquid and liquid-liquid systems as a function of composition.

The dielectric constant of a solid substance in the dissolved state may be found by using a solvent with a dielectric constant that remains invariable when the solid substance is dissolved. The slope values obtained from dielectric constant versus concentration plots of the solid substance in two solvents with different dielectric constants are extrapolated or interpolated. The dielectric constant of a solid substance in the dissolved state also can be found directly from the dielectric constants of solutions of the solid in one solvent at two concentrations. The dielectric constants are converted to polarizations, and the two values allow calculations of the polarizations of the solvent and solute separately. From the polarization of the solute, one can calculate its dielectric constant (in dissolved state). Such a procedure is correct only if the dielectric constant is concentration independent.

Chemistry, Pharmaceutical↗
PubMed1978

Relationship between osmolality and osmolarity.

Since the compendia require the osmolarity of certain parenterals to be labeled and since experimentally only the osmolality can be measured, it is necessary to obtain the relationship between these two quantities. This relationship was determined by considering fundamental physical-chemical definitions. The osmolality of a solution was found to be simply related to the osmotic coefficient. The conversion to osmolarity requires the use of the partial molal volume(s) of the solute(s). A single conversion factor is required for a particular solute system; i.e., the conversion factor is independent of the solution concentration.

Chemical Phenomena↗
PubMed1978

Ball milling as a measure of crushing stength of granules.

When granules are milled in a ball mill, the size decrease follows a modification of Kick's law. The Briggsian decay constant, here denoted as the attritional crushing strength, shows correlation with the Harwood-Pilpel crushing strength. Both crushing strengths show a correlation with the amount of granulating agent (povidone) added to the granulation, i.e., the more povidone added, the harder the granule.

Methods↗
PubMed1978

USP dissolution III: semilogarithmic dissolution patterns of tablets in rotating-basket assemblies.

The dissolution of a rapidly soluble, finely subdivided substance in a directly compressed tablet and in a wet granulated tablet was treated experimentally and compared with previous theoretical models. The dissolution curves were sigmoid with a semilogarithmic tail when concentration was plotted versus time. As predicted, the slope of the semilogarithmic plots were related to the disintegration decay constant for tablet erosion in the basket.

Models, Chemical↗
PubMed1978

USP dissolution IV: comparison of methods.

The hydrodynamics of four dissolution apparatus--viz., the USP basket, the USP paddle, the stationary basket-spinning filter, and the USP disintegration apparatus, were characterized. At higher velocities, the relationship between the intrinsic dissolution rate constant and linear velocity was parabolic rather than linear.

Chemistry, Pharmaceutical↗
PubMed1977

Flow rates and repose angles of wet-processed granulations.

The equation of McDougall and Evans was found not to apply to granulations. The functional relationships among volumetric powder flow rates, angles of repose, and particle size were demonstrated to exhibit maxima (rather than minima) in five common pharmaceutical granulations produced by wet processing. The angular behavior of granules (such as the experienced range of angles) is explained via supported stacking geometries, and the shallow maxima in the angle of repose versus granule diameter was derived from this model.

Chemistry, Pharmaceutical↗
PubMed1977

Influence of granulation liquid flow rate on particle-size distribution in spray-granulate products.

Granulations were made at various air speeds and various rates of addition of granulating liquid in a spray-granulatin assembly. The ensuring particle sizes were log-normal, and the data substantiate that the process is of the nature previously described. The mean diameter obtained was approximately proportional to the liquid flow rate squared but was independent of air rate. The standard deviation was independent of both parameters.

Drug Compounding↗