Biomedical subjects

R Bodmeier

Publications and source records attributed to R Bodmeier.

59 records · Page 4Linked to original sources

PubMedDate not supplied

Polylactic acid microspheres containing quinidine base and quinidine sulphate prepared by the solvent evaporation method. III. Morphology of the microspheres during dissolution studies.

Poly(dl-lactide) (PLA) microspheres containing quinidine or quinidine sulphate were prepared by the emulsification-solvent evaporation technique. The in vitro release profile of quinidine or quinidine sulphate from the microspheres was characterized by three phases: a lag time, a rapid release phase (burst), and a slow release phase. Drug release was studied as a function of the ionic strength of the dissolution medium, to demonstrate the importance of the water imbition into the microspheres which induced the drug release. The lag time increased with increasing ionic strength. The microspheres stayed intact during the dissolution study as shown by scanning electron microscopy (SEM). Disintegration of microspheres which was initially observed was an artifact introduced during the SEM procedure. The high vacuum applied either during the coating of the microspheres with gold-palladium or during the actual observation in the scanning electron microscope caused the microspheres to collapse or rupture.

Chemical Phenomena↗

PubMedDate not supplied

Encapsulation of water-soluble drugs by a modified solvent evaporation method. I. Effect of process and formulation variables on drug entrapment.

Pseudoephedrine HCl, a highly water-soluble drug, was entrapped within poly (methyl methacrylate) microspheres by a water/oil/water emulsification-solvent evaporation method. An aqueous drug solution was emulsified into a solution of the polymer in methylene chloride, followed by emulsification of this primary emulsion into an external aqueous phase to form a water/oil/water emulsion. The middle organic phase separated the internal drug-containing aqueous phase from the continuous phase. Microspheres were formed after solvent evaporation and polymer precipitation. The drug content of the microspheres increased with increasing theoretical drug loading, increasing amounts of organic solvent, polymer and polymeric stabilizer, and decreased with increasing stirring time, increasing pH of the continuous phase and increased volume of the internal and external aqueous phase.

Delayed-Action Preparations↗

PubMedDate not supplied

Spontaneous formation of drug-containing acrylic nanoparticles.

Nanoparticles containing ibuprofen, indomethacin or propranolol were formed spontaneously after the addition of solutions of the drugs and acrylic polymers (Eudragit RS or RL 100) in the water-miscible solvents, acetone or ethanol, to water without sonication or microfluidization. The colloidal dispersions were stabilized by quaternary ammonium groups and did not require the addition of surfactants or polymeric stabilizers. The nanoparticles were compared to nanoparticles prepared either by a microfluidization-solvent evaporation method with a water-immiscible organic solvent, methylene chloride, or by a melt method with respect to particle size and redispersibility of freeze- or spray-dried samples. Nanoparticles prepared by microfluidization or the melt method were easily redispersed while Eudragit RS nanoparticles prepared by spontaneous emulsification were not redispersible. Flexible films were formed from the nanosuspensions after the addition of 15 per cent triethyl citrate, a water-soluble plasticizer. The release of propranolol from the films increased with increasing proportion of RL, but was independent of the order of mixing of the two polymers or nanosuspensions during film preparation. The drug release from indomethacin films was increased by adding water-soluble polymers to the nanosuspension.

Acrylates↗

PubMedDate not supplied

Process and formulation variables in the preparation of wax microparticles by a melt dispersion technique. I. Oil-in-water technique for water-insoluble drugs.

Ibuprofen-wax (carnauba, paraffin, beeswax, and the semisynthetic glyceryl esters--Gelucire 64/02 and Precirol ATO5) microparticles were prepared without organic solvents as an alternative to polymeric microparticles. In the melt dispersion technique, the drug-wax melt was emulsified into a heated aqueous phase followed by cooling to form the microparticles. The microparticles were characterized with respect to their drug loading, and morphological and release properties. They were spherical and non-agglomerated and drug loading close to 60 per cent were achieved. The more hydrophilic waxes (Gelucire 64/02 or Precirol ATO5) could be prepared without the use of surfactants. With the other waxes, increasing amounts of sodium lauryl sulphate in the external aqueous phase decreased the drug loading because of drug solubilization when compared to the polymeric stabilizer, poly(vinyl alcohol). The type of wax, the rate of cooling, and the temperature of the aqueous phase had no significant effect on the drug loading because of the low solubility of the drug in the external aqueous phase. The drug release was controlled by the hydrophobicity of the wax. Besides ibuprofen, other water-soluble drugs (ketoprofen, indomethacin, hydrocortisone) were also encapsulated by this method. The wax microparticles could be formulated into an aqueous sustained-release oral suspension dosage form.

Delayed-Action Preparations↗

PubMedDate not supplied

Process and formulation variables in the preparation of wax microparticles by a melt dispersion technique. II. W/O/W multiple emulsion technique for water-soluble drugs.

Pseudoephedrine HCl-carnauba wax microparticles were prepared by a multiple emulsion-melt dispersion technique. A heated aqueous drug solution was emulsified into the wax melt (W/O emulsion), followed by emulsification of this primary emulsion into a heated external aqueous phase (W/O/W emulsion). The drug-containing microparticles were formed after cooling and congealing of the wax phase. The encapsulation efficiencies were above 80 per cent and actual drug loadings close to 50 per cent were achieved. The surface of the microparticles had submicron pores and drug crystals were visible on cross-sections. The drug loading depended on the rate of cooling and the volume of the internal aqueous phase but was insensitive to the volume of the continuous phase. The drug release was much faster when compared to the release from polymeric microspheres.

Drug Compounding↗