C.W. Whitworth

Preparation and Evaluation of Controlled Release Indomethacin Microspheres

AbstractMicrospheres containing indomethacin were prepared with various combinations of polymers Eudragit RS and Eudragit L. The effects of different ratios of polymers, solvent-polymer ratio, polymer-drug ratio and evaporation temperature on the physical characteristics of the microspheres as well as the in vitro release rate of the drug were investigated. All the factors studied had an influence on the physical characteristics of the microspheres. In vitro dissolution results showed that all formulations gave prolonged release of indomethacin and the release followed apparent zero order kinetics until 80% of drug had been released.

Control of Drug Release Rate by Use of Mixtures of Polycaprolactone and Cellulose Acetate Butyrate Polymers

AbstractChlorpromazine microspheres were prepared by an emulsion solvent evaporation technique using polycaprolactone and cellulose acetate butyrate as the matrix. The fluidity of the polymer solution was easily adjusted by use of mixtures of two polymers and thus provided a practical means to control the microsphere size. The In Vitro release pattern was easily changed by changing the ratios of these two polymers. An increase in polycaprolactone content of the polymer microsphere matrix brought about an increase in the release rate. Drug loading had no predictable effect on the dissolution rate, but smaller microspheres gave more rapid drug release due to the greater surface area.

Dissolution Characteristics of Polycaprolactone-Polylactide Microspheres of Chlorpromazine

AbstractStudies were conducted on the preparation of controlled release polycaprolactone-polylactide microcapsules of chlorpromazine and on release of the drug from the microcapsules in pH 7.0 buffer medium. A wide range of release rates of the drug was obtained by simple change in the polymer system. Chlorpromazine was released from the microspheres in a biphasic manner consisting of an initial fast release phase followed by a slow-release phase. Increasing the drug content increased the initial drug release rate but no significant drug loading effect on the second stage dissolution rate was noted. There was no significant effect of particle size on the drug release rate from the microspheres. The swelling property of the microspheres and the agglomerate nature of the sieve fractions may complicate the drug release kinetics and obscure the particle size effect on dissolution rate.

Effect of Process Variables on Drug Release from Microparticles Containing A Drug-Resin Complex

AbstractMicroparticles consisting of dextromethorphan-resin complex (resinate) coated with a cellulose derivative were prepared by a modified emulsion-solvent evaporation method. Adjustment of the release rate was achieved by varying resinate (core) to polymer (coat) ratio or by using additives. Higher ratios of resinate to polymer gave faster release of the drug. Polyethylene glycol (PEG) 4000 also increased the release rate. Increasing core to coat ratio also increased average particle size. Placing the emulsifying agent in different phases of the emulsion in the fabrication process also affected the particle size distribution. The microparticles showed good sustained release of the drug

Compression of Miczocwsules II: Effect of Excipients and Pressure on Physical Propertise accordance with their physical properties

AbstractDmg-resin carplexes were microencapsulated and cmpressed into tablets with the aid of various excipients. Carpression of the microcamules at pressures ranging fran 35 MPa to 281 MPa produced tablets of acceptable physical properties only with Avicel. When Rdex or Fast Flo Lactose were used an unacceptably high tablet friability was seen. The tablet porosities varied in

Compression of Microcapsules I: Effect of Excipients and Pressure on Drug Release

AbstractMicrocapsules containing phenylpropanolamine-resin complexes were compressed with various diluents. Compression of microcapsules produced an increase in the release rate. An average reduction of 0.50 hours was observed when Emdex or Fast Flo Lactose were compared to Avicel at various pressures (35 to 281 MPa). Increasing the amount of microcapsules in the formulation reduced the T50% with all three diluents

Microencapsulation by Emulsion Non-Solvent Additicin Method

AbstractCellulose acetate butyrate microcapsules containing propranolol were prepared by emulsion non-solvent addition method. The effects on drug release of different polyethylene glycols (PEG), various concentrations of PEG 4000, and particle size of the drug to be encapsulated were investigated. In vitro dissolution of microcapsules in simulated intestinal fluid and buffers at different pH was also studied. PEGs were found to increase drug release for this system. The pH dissolution profiles of the microcapsules indicated that dissolution was slightly pH dependent during the first 8 hours of dissolution.

Ehancement of Dissolution Rate by Incorporation into a Water Insoluble Polymer, Polycaprolactone

AbstractThis report concerns the use of water insoluble polymer, polycaprolactone, as a carrier to enhance the dissolution rate of two drugs, chlorpromazine and progesterone. Polycaprolactone microspheres containing these drugs were prepared by an emulsion-solvent evaporation technique and dissolution characteristics were compared to pure drug.Dissolution studies revealed that both chlorpromazine-poly-caprolactone and progesterone–polycaprolactone microspheres exhibited a faster dissolution rate than the pure drugs. Molecular or colloidal dispersion of drugs in the polycaprolactone microshere matrix and the high permeability of polycaprolactone to the drugs and water are possible reasons for the rapid release perties observed.

Aspirin Degradation in Mixed Polar Solvents

AbstractDegradation studies were conducted on 0.2% w/v aspirin liquid formulation in a wide range of water-propylene glycol mixtures and water-triethylene glycol diacetate mixtures at four temperatures. The effect of a surfactant, polyoxyethylene (20) sorbitan monolaurate, on aspirin stability was also investigated. There was a linear relationship between water content and degradation rate constants. The surfactant increased aspirin degradation in all formulations. Formulations containing the higher concentration of the surfactant showed the greater aspirin decomposition.