PubMed Health⌕ Search

Biomedical subjects

N Pilpel

Publications and source records attributed to N Pilpel.

At least 37 records · Page 2Linked to original sources
PubMed1984

Simple, rapid method for comparing the self-emulsifiability of hydrocarbon oils.

A simple and rapid method for comparing the degree of self-emulsifiability of different hydrocarbon oils is described. The method involved measurement of the intensity of light scattered at an angle of 31 degrees to the incident radiation by the sample. The extent or degree of self-emulsification of selected hydrocarbon oils was observed to be affected by the nature of the oil as well as by the type and concentration of the surfactants employed. The method is useful when screening surfactant-hydrocarbon oil combinations as potential vehicles for drugs in the pharmaceutical industry or herbicides and pesticides for agricultural purposes.

Chemical Phenomena↗
PubMed1984

Tensile strengths of paracetamol and Avicel powders and their mixtures.

Measurements were made of the tensile strengths of paracetamol and Avicel powders and of their mixtures. Two quantities were derived from the results; m, a universal constant whose value was 1.00 +/- 0.23 and alpha, a constant of the material. The value of alpha for paracetamol was much larger than that for Avicel and increased slightly with increase in particle size. Adding 25% w/w of Avicel to paracetamol produced a significant decrease in alpha and this fact may account for its use as an excipient in the tableting of paracetamol.

Acetaminophen↗
PubMed1984

Plasto-elasticity and tableting of paracetamol, Avicel and other powders.

The plasto-elasticity of mixtures of paracetamol and Avicel powders and the tensile strengths of their tablets varied with the sizes of the particles and with the compositions of the mixtures. Tests made on these and other tablets showed that the logarithms of their strengths were inversely proportional to the ratios of the samples' elastic recovery: plastic compression; they exhibited lamination or capping when this ratio was greater than 9.

Acetaminophen↗
PubMed1984

Complexation of tetracyclines with metal ions in relation to photosensitization.

It has been shown by spectroscopy and by a Photosensitive Index method, involving measurements of interfacial tension, that Cu2+ and Ni2+ form 2:1 complexes with oxytetracycline and 1:1 complexes with demethylchlortetracycline. Fe2+, Zn2+, Mg2+ and Ca2+ form weaker 1:1 complexes with both drugs. The possibility is discussed of using metal ions to reduce photosensitization by tetracyclines in-vivo.

Chemical Phenomena↗
PubMed1983

Effects of ultraviolet light on lecithin monolayers in the presence of fluorescein dyes and tetracycline drugs.

A Langmuir trough was employed to measure the effects of u.v. irradiation on the force area characteristics of monolayer films of lecithin spread on aqueous solutions of some dyes and tetracycline drugs both in the absence and presence of Ca2+ and Ni2+. Irradiation caused photochemical reactions which resulted in the expansion of the films and the extent of reaction was measured by the Photosensitive Indices. The reaction with tetracyclines was inhibited by adding Cu2+ or Ni2+ to the substrate. The kinetic orders of the reactions are given.

Copper↗
PubMed1983

Tensile strength and compression of coated pharmaceutical powders: tablets.

A study has been made of the tensile strength and compression during tableting of lactose, sodium chloride and calcium phosphate powders after they had been coated with small amounts of stearic acid, polyethylene glycols and polyvinylpyrrolidones. The properties of the systems were measured over a range of temperatures. The tensile strength and the compression behaviour depended not only on the amount and type of the coating material but also on the homologous temperature of processing. The changes in tensile strength have been explained in terms of changes in interparticle separation, changes in interparticle forces and the formation of welded bonds by the coatings. The compression results have been analysed in terms of the Heckel and the Cooper & Eaton equations.

Drug Compounding↗
PubMed1983

Photosensitization by fluorescein dyes and tetracycline drugs at an oil/water interface.

Measurements were made of the changes that occur in the interfacial tension of isopropylbenzene when floating on water containing between 10(-5) and 10(-3) M of various fluorescein dyes and tetracycline drugs and irradiated for up to 240 min with ultraviolet light. Singlet oxygen was found to be an active intermediate in the reactions. The results are discussed in relation to adverse photosensitization in-vivo due to fluorescein dyes and tetracycline drugs.

Chemical Phenomena↗
PubMed1983

Absorption of moisture by sodium cromoglycate and mixtures of sodium cromoglycate and lactose.

The presence of up to about 15% w/w moisture has little effect on the tensile and shear properties of sodium cromoglycate and of 1:1 mixtures of sodium cromoglycate and lactose. Analysis of their adsorption and desorption isotherms using equations developed by Young and Nelson shows that this is because most of the moisture is absorbed into the interior of the sodium cromoglycate leaving little absorbed moisture on the surfaces of the particles concerned.

Absorption↗
PubMed1982

Effects of paraffin coatings on the tensile strength of lactose.

Measurements have been made of the tensile strength of lactose at different temperatures after coating it with up to 10(-4) mol of various paraffin hydrocarbons g-1 of powder. Providing the coating is in a liquified form, either as a result of the ambient temperature or because of the localized high pressure at the points of true contact between the particles, there is a correlation between the tensile strength of the powder and the thickness and viscosity of the coating layer.

Chemistry, Pharmaceutical↗
PubMed1982

Effects of paraffin coatings on the shearing properties of lactose.

An annular shear cell has been employed to measure the shearing properties of lactose powder coated with up to 10(-4) mol g-1 of powder of a series of paraffin hydrocarbons. The angle of internal friction, delta, of the coated powders was independent of their packing density. The shearing properties of the powders depended on the concentration, the viscosity and thickness of the coating material.

Chemical Phenomena↗
PubMed1981

Effect of temperature changes on the densification and compression of griseofulvin and sucrose powders.

A study has been made of the effect of varying the temperature between - degree and -25 degree C on the densification and low pressure compression of griseofulvin, sucrose and mixtures of the two powders. Densification and compression of the materials were facilitated as they were cooled in the range of homologous temperatures (ratio of the experimental temperature in degree K to melting point of the material in degree K) from 0.7 to 0.5. This was attributed to a reduction in the cohesive forces operating between the particles. Values are given for the activation energies of densification and compression derived by plotting the logarithms of these properties versus the reciprocal of the absolute temperature. For both materials and their mixtures the activation energies were in the range of about 1 to 10kJ mol-1 showing that physical rather than chemical forces were operating between the particles.

Griseofulvin↗
PubMed1980

Cooling as a possible method for increasing the flowability of certain pharmaceutical and other powders.

Measurements have been made of the rates of flow under gravity of powdered sugars and of fatty acids through circular orifices at temperatures between -25 and 110 degrees C. The flow rates decrease considerably as the powders are heated; conversely they increase as the powders are cooled from a high ambient temperature of 40 to -25 degrees C. The results are ascribed to changes in the cohesiveness of the powders caused by softening and plastic deformation of particles at elevated temperatures. Lactose, paracetamol and griseofulvin granule formations have been reported to show similar effects and the possibility is discussed of using cooling to increase the flowability of particular powders in pharmaceutical production. The rates of flow of the powders are given by the expression(formula: see text)where W is the flow rate in g min-1, Do is the orifice diameter in cm, rho is the particle density in g cm-3, g is the gravitational constant, and A and n are numerical terms which depend on temperature and particle size.

Cold Temperature↗
PubMed1978

Factors affecting the disintegration and dissolution of chloroquine phosphate/starch tablets.

A study has been made of the effects produced on the disintegration and dissolution times of chloroquine phosphate tablets by varying their moisture and starch contents and the distribution of the starch in the formulation. 3 to 5% w/w of moisture produces a maximum in the disintegration and dissolution times. Starch added externally as a powder acts only as a disintegrating agent for the tablets, but starch added internally as a paste during granulation acts both as a binding agent and a disintegrant.

Chemistry, Pharmaceutical↗
PubMed1978

Effects of temperature on the tensile strength of pharmaceutical powders.

Measurements have been made of the tensile strengths of fatty acids, lactose and of an oxtetracycline and a paracetamol tablet formulation at temperatures between -20 and +90 degrees. The measurements were made on compressed tablets and on consolidated beds of powders, using a diametral compression tester and a split plate tensile tester which had been designed to operate over this range of temperature. The tensile strengths of all the materials increase with temperature and values are given for the activation energies of bonding between particles.

Acetaminophen↗
PubMed1978

The effect of the photodecomposition of chlorpromazine on lecithin monolayers.

Chlorpromazine hydrochloride (cpz) is decomposed when irradiated with ultraviolet light, forming H+, hydrochloric acid, chlorpromazine sulphoxide and 2-hydroxypromazine. The order of the reaction (as measured by the expansion that is produced in a lecithin/cpz monolayer) varies between zero and about 3/4. The results have been used to explain some of the adverse side effects that are observed when patients are treated with cpz.

Chemical Phenomena↗
PubMed1977

Formulation factors affecting strength and dissolution of uncoated oxytetracycline tablets.

The effect of various formulation and processing factors on the properties of 300-mg oxytetracycline tablets was studied. At a constant moisture level and packing fraction, an increase in gelatin concentration resulted in increased tensile strength, increased disintegration and dissolution times, and reduced capping tendency. The Wagner theory of dissolution applied satisfactorily to tablets containing up to 5% (w/w) gelatin but was less applicable at higher gelatin levels. Dissolution rate constants were calculated, and their values depended on the gelatin content and packing fraction of the tablets.

Drug Compounding↗