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Biomedical subjects

C F Lerk

Publications and source records attributed to C F Lerk.

At least 55 records · Page 3Linked to original sources
PubMed1983

Improvement by super disintegrants of the properties of tablets containing lactose, prepared by wet granulation.

The crushing strength, disintegration and dissolution properties of tablets, made by wet granulation with lactose as filter, gelatin as binder, potato starch as disintegrant and magnesium stearate as lubricant can be markedly improved when the potato starch (20%) is replaced by a much lower concentration (4%) of an insoluble super disintegrant, such as sodium starch glycolate (Primojel) or crospovidone (Polyplasdone XL). The incorporation of partially water soluble super disintegrants such as low-substituted sodium carboxymethylcellulose (Nymcel, ZSD 16), causing a viscous barrier in the tablets when containing water, is shown to be deleterious for both tablet disintegration and drug release. In contrast to potato starch, the position of the super disintegrants (intragranular, extragranular or equally distributed) had hardly any effect on the tablet properties. The improved properties of the tablets containing insoluble super disintegrants, when compared to tablets with potato starch, are the result of the use of a much lower concentration of disintegrant, but especially of the difference in effect of magnesium stearate on the disintegration capacity of the slightly swelling potato starch and the strongly swelling super disintegrants, respectively. The latter cause, even in the presence of the liquid penetration inhibiting hydrophobic magnesium stearate, a chain reaction of opening of the tablet, starting at the outside and resulting in a fast disintegration.

Excipients↗
PubMed1983

Novel techniques for determination of antibacterial activity of silver sulfanilamides.

By means of suspension techniques, MIC's of ten silver sulfanilamides against fifty-six different strains of bacteria were determined. The only two bacteria which were sensitive were Streptococcus pyogenes and Escherichia coli. The local application of these drugs in burn patients only reduces colonization. The cream base is probably also involved in the anticolonization effect.

Anti-Bacterial Agents↗
PubMed1982

Studies on different dissolution models. IV. Erosion of tablets.

A comparative study of the action of erosion on non disintegrating theophylline tablets was performed in the three USP XX dissolution models, the rotating basket, the paddle and the modified disintegration apparatus, as well as in a new (sandwich) model. The results show erosion to be dependent on the mechanical strength of the tablets and to be promoted by the phenomenon of softening of the tablets during the process of dissolution. A considerable and moderate erosion was found for 'soft' tablets in the rotating basket and disintegration apparatus, respectively, whereas no or only slight erosion was observed in the paddle and sandwich models. The phenomenon of dissolution intensified erosion and erosion intensified dissolution is shown to affect the description of the release profiles. The dissolution profiles of the 'hard' tablets in the models preferred to be described by the square root equation, whereas the profiles of the 'soft' tablets in the case of erosion showed a tendency to a better fit with the cube root of mass versus time relation.

Kinetics↗
PubMed1981

Interaction of tablet disintegrants and magnesium stearate during mixing I: Effect on tablet disintegration.

The effect of magnesium stearate on the disintegration of tablets was studied. Three different preblends, containing a slightly or a strongly swelling disintegrant, were mixed before compression with magnesium stearate for different time periods. The results show that a strongly swelling disintegrant, such as sodium starch glycolate in contrast to potato starch, can reduce the deteriorating effect of hydrophobic lubricants on tablet disintegration. However, the interaction between magnesium stearate and potato starch or sodium starch glycolate and the resulting differences in disintegration characteristics can be masked by the use of disks in the USP disintegration apparatus.

Aspirin↗
PubMed1979

Effect of microcrystalline cellulose on liquid penetration in and disintegration of directly compressed tablets.

The penetration of isooctane and water into tablets of microcrystalline cellulose, dibasic calcium phosphate dihydrate, spray-crystallized maltose-dextrose, and blends of microcrystalline cellulose with one of the other excipients were studied. The isooctane penetrations occurred according to the Washburn equation and were not affected by the presence of 0.5 or 1.0% magnesium stearate. The inhibition of aqueous penetration into tablets resulting from hydrophobic magnesium stearate was less pronounced for vehicles like dibasic calcium phosphate, which exhibited extensive brittle fracture under compression. Microcrystalline cellulose tablets, both with and without magnesium stearate, exhibited extremely fast aqueous penetration even at low porosities, caused by breaking of the hydrogen bonds and subsequent widening of the pores. Ratios between water uptake and original pore volume up to 20 were obtained for microcrystalline cellulose tablets. This unique property was, however, suppressed by the presence of fast dissolving and highly soluble excipients like dextrose, resulting in an antagonistic disintegration behavior of tablets compressed at pressures over 10,000 N/cm2. Improved disintegration properties were obtained by blending microcrystalline cellulose with an insoluble vehicle such as dibasic calcium phosphate dihydrate.

Calcium Phosphates↗
PubMed1979

In vitro and in vivo availability of hydrophilized phenytoin from capsules.

The effect of phenytoin hydrophilization on the liquid penetration rate into prepared plugs, on the disintegration time, on the in vitro release rate, and on in vivo absorption in humans was studied. Hydrophilization was performed by intensive mixing of the hydrophobic drug with a small amount of methylcellulose solution. Liquid penetration into the treated plugs was independent of the liquid wetting potency and extremely high compared to the pure drug plugs. Analogous results were obtained for the disintegration time and in vitro release rates from capsules loaded with pure and treated drug. A bioavailability study in seven healthy volunteers showed immediate absorption of the treated drug but a 1-hr absorption lag time for the pure drug.

Adult↗
PubMed1978

Effect of hydrophilization of hydrophobic drugs on release rate from capsules.

The release of poorly soluble hydrophobic drugs from capsules can be improved significantly by the creation of a hydrophilic surface by intensive mixing of the hydrophobic drug with a small amount of a solution of a hydrophilic excipient. This technique was introduced previously for the production of microgranules. The data presented indicate that the hydrophilic material is mechanically distributed over the hydrophobic surface. The creation of hydrophilic capillaries in a capsule or tablet allowed the rapid penetration of the dissolution fluid, resulting in a dispersion of well-wetted particles, so that the maximum surface area of the powder was exposed to the dissolution medium. Moreover, hydrophilization of hydrophobic drugs has the important benefit that the release rate from capsules is independent of the surface tension of the dissolution medium.

Capsules↗
PubMed1977

Contact angles of pharmaceutical powders.

Contact angles of pharmaceutical powders were determined by measuring the maximum height of a drop of a saturated solution on a presaturated compact of the material. The results for a series of drugs are presented.

Capsules↗
PubMed1976

Contact angles and wetting of pharmaceutical powders.

Contact angles of pharmaceutical powders were determined by the h-epsilon method, which consists essentially of measuring the maximum height of a drop of liquid fomed on a presaturated compact of the material. Determinations with aspirin as the test material indicate that the measured value is independent of the particle size of the powder and the porosity of the cake. The method was extended to include determinations on mixed powder systems. The results show that the hydrophobic material dominates with large particle-size powders; with small particle sizes, a linear relationship between the cosine of the contact angle of the mixed system and the proportion of the components is obtained. Results are presented for a wide variety of materials of pharmaceutical interest.

Aspirin↗