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Biomedical subjects

C J De Blaey

Publications and source records attributed to C J De Blaey.

10 recordsLinked to original sources
PubMed1984

Pulsed proton NMR and solid-liquid fat ratio determinations in suppository vehicles and aminophylline suppositories.

The physical state, melting behaviour and release rate of aminophylline suppositories were studied during storage. The fraction of non-crystallized fat, assessed by pulse NMR, varies between different vehicles. At room temperature several vehicles do not seem to be completely crystalline. Aging, as observed in prolonged melting time and a reduced release rate, is not expressed in a drastic reduction of the fraction of non-crystallized fat, as observed by NMR. On the contrary the mobility of the protons in the non-crystallized state is likely to offer a more promising tool to monitor aging.

Aminophylline↗
PubMed1984

Prolonged storage of aminophylline suppositories. The impact on physical parameters and bioavailability.

Prolonged storage of aminophylline/cocoa butter suppositories at 30 degrees resulted in a marked decrease in bioavailability, after administration to a panel of human volunteers. Not more than 20% of the drug content was absorbed during the first 8 hours and the maximum plasma level was obtained 5-7 hours after administration. It was concluded that storage conditions should be considered well and storage instructions should be given to the patient.

Aminophylline↗
PubMed1984

A new approach of ordered mixing applied to digitoxin tablets.

In ordered mixing it is assumed that mixing very different amounts of two materials is improved by adsorption of small particles onto large carrier particles. This hypothesis could be confirmed with tablets of 120 mg containing 0.1 mg digitoxin, prepared by dry coating of particles.

Adsorption↗
PubMed1984

Dissolution at porous interfaces VI: Multiple pore systems.

With the aid of rapidly dissolving sodium chloride particles, cubic pores were made in the surface of a theophylline tablet. The influence of the pores on the dissolution rate of the surface was investigated in a rotating disk apparatus. Like the drilled pores used in earlier studies, downstream on the surface they caused a turbulent flow regimen with the development of a trough due to enhanced erosion. The phenomenon of a critical pore diameter, discovered with single, drilled pores, seems to be applicable to the cubic pores investigated in this study, although a higher degree of surface coverage with pores caused complications, probably due to particles bordering one another and forming larger pores. The behavior of the porous surfaces at different rotation speeds was studied. Due to the presence of pores the laminar character of the boundary layer flow changes to turbulent, which induces locally an increased dissolution flux in the wake of a pore.

Particle Size↗
PubMed1983

Dissolution at porous interfaces. IV. Pore effects in natural convection flow.

The dissolution rate of a nicotinic acid tablet surface was measured in a dissolution system where mass transport in the solvent is governed by a combination of natural and forced convection. While such experimental conditions were chosen that natural convection outweighted forced convection, the dissolution rate increasing effect of large pores in the tablet surface was studied. To that end cylindrical pores were drilled into the tablet. The increase in dissolution rate was measured as a function of the number of pores, their depth and diameter and their position with respect to each other and to the centre of the dissolving surface. The results are discussed with regard to the hydrodynamic conditions near the pores. In addition to the regularly arranged cylindrical pores a more irregular configuration of cubic pores was investigated. These pores were created by embedding cubic sodium chloride crystals in the tablet surface during the compression procedure. After the sodium chloride particles had dissolved rapidly a porous surface of much slower dissolving nicotinic acid remained. The dissolution rate of the porous surface was determined and a comparison was made between surfaces with and without pores of several sizes.

Nicotinic Acids↗
PubMed1983

In vitro testing of controlled release theophylline preparations: Theolair, Theograd and Theolin.

Three dissolution methods, i.e. a paddle type, the USP disintegration and a column method, were used to characterize the release from three controlled release theophylline preparations, i.e. Theolair Retard 250, Theolin Retard 300 and Theograd 350. The release profiles proved to be dependent upon agitation intensity and pH or a combination of both, but the sensitivity towards these variables differed markedly between the products tested.

Delayed-Action Preparations↗
PubMed1982

Drug release from non-aqueous suspensions. I. Release of phenobarbital and phenobarbital sodium from paraffin suspensions.

The rate at which phenobarbital and phenobarbital sodium, suspended in liquid paraffin, are released to buffers pH = 3.0, 7.4 and 10.0 has been studied. The release rate of phenobarbital depends on its solubility and hence on the pH, whereas the initial release rate of phenobarbital sodium is governed by sedimentation and hence is independent of the pH. However, when phenobarbital sodium is released to buffer pH = 3.0, it crystallizes in the interfacial layer after an initial release time. The release process in the release apparatus used cannot be described by a theory based on forced convection [i.e. the (E)SCRD-theory], but has to be regarded as a natural convection process.

Chemistry, Pharmaceutical↗