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Biomedical subjects

P York

Publications and source records attributed to P York.

67 records · Page 4Linked to original sources
PubMed1978

Particle slippage and rearrangement during compression of pharmaceutical powders.

Compression data from different size fractions of lactose, chloroquine diphosphate, stearic acid and calcium carbonate have been analysed using the Walker and the Heckel compression equations. Points of inflection in graphs of log applied pressure vs the reciprocal of the packing fraction at low pressures corresponded closely to figures for theoretical packing conditions for equisized spheres and are attributed to a change in the stage of compression. The degree of particle slippage and rearrangement taking place during compression has been shown to increase as the particle size of the powder decreases and to be more extensive for powders composed of non-spherical particles. In addition, three types of compression behaviour have been distinguished for the four powders studied.

Calcium Carbonate↗
PubMed1977

Dimensional changes of compacts after compression.

A non-contact optical technique has been used to measure changes in the heights and diameters of compacts prepared from sodium chloride, spray dried lactose, two samples of methylcellulose powder and two spray-dried lactose-maize starch granulations. Both sodium chloride and spray dried lactose exhibited relatively small dimensional changes whilst the methylcellulose powders showed up to 30% axial and 3% radial expansion. The results are discussed in terms of the inherent properties of the materials. When the lactose was granulated with maize starch, the ratio of axial; radial strain recovery was reduced from 5-9:1 to approximately 1:1, suggesting an improved distribution of forces during compression of the granulations,

Drug Compounding↗
PubMed1977

The shelf life of some antibiotic preparations stored under tropical conditions.

Accelerated storage tests have been carried out to predict the shelf life of several commercial preparations stored directly under temperate and tropical climatic conditions. Two brands each of sulphathiazole tablets, tetracycline hydrochloride capsules and chloramphenicol capsules were studied over a period of three months. Shelf lives ranging from 6.2. to 29.7 months were predicted for temperate storage conditions (20 degree C/31% R.H.), whilst these periods were reduced giving values from 3.8 to 13.9 months for tropical conditions of 30 degree C/31% R.H and from 2.5 to 9.2. months when stored at 30 degree C/75% R.H. A decrease in the rate of drug dissolution was also observed for preparations stored directly under conditions of elevated temperature and humidity. The results indicate the need for stringent control over storage conditions for antibiotic preparations in tropical climates to ensure adequate drug stability and dissolution characteristics.

Anti-Bacterial Agents↗
PubMed1976

Modification of diffusion rates of benzocaine from topical vehicles using sodium salicylate as complexing agent.

The release of benzocaine from various topical vehicles containing benzocaine, alone and in the presence of a complexing agent, sodium salicylate, was measured at 37 degrees using dialysis through a cellulose membrane. Sodium salicylate had a marked effect on the release of benzocaine, depending upon the the type of vehicle, with the largest increase observed for the water-miscible base, polyethylene glycol (macrogol ointment BPC). The amount of drug released from preparations containing 1% (w/w) and 2% (w/w) benzocaine in this vehicle depended upon the sodium salicylate concentration. Results are discussed in terms of the differing physical properties of the complexes formed.

Benzocaine↗
PubMed1976

A preliminary study of the physical stability of tablets prepared from powders stored under tropical conditions.

A study has been made of the effects of storing powders under tropical conditions before compression on the physical stability of the tablets prepared from them, as measured by changes in tablet weight, volume and hardness. Significant changes in stability have been observed and these have been related to the different degrees of moisture uptake by the powders during storage. In addition, the initial powder storage conditions have been shown to be important when considering the best method of tablet manufacture with respect to tablet stability.

Drug Stability↗
PubMed1975

Application of powder failure testing equipment in assessing effect on glidants on flowability of cohesive pharmaceutical powders.

Powder failure testing equipment was used successfully to study the effect of glidants on the flowability of two cohesive pharmaceutical powders, lactose and calcium hydrogen phosphate, using the flow factor as the flowability parameter. Fine silica, magnesium stearate, and purified talc were investigated as glidants; for each host powder-glidant mixture, an optimum concentration of glidant was observed beyond which no further increase in flowability occurred. The order of efficiency of glidants for both host powders was fine silica greater than magnesium stearate greater than purified talc. The mode of action of the three glidants is discussed.

Calcium Phosphates↗