Peter J. Stewart

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The aim of this study was to investigate the effect of coating on the aerosolization of three model micronized powders. Three model powder materials (salbutamol sulphate, salmeterol xinafoate, triamcinolone acetonide) were chosen not only for their different chemical properties but also for their different physical properties such as shape and size(More)
Interactive mixtures were prepared containing 5% (w/w) salbutamol sulfate using various lactose carrier systems, including sieved fractions and blended mixtures of coarse and fine particles. The solid state and powder properties of the lactose carriers were examined by laser diffraction, differential scanning calorimetry, thermogravimetric analysis, powder(More)
Purpose. The role of fine lactose in the dispersion of salmeterol xina- foate (SX) from lactose mixtures was studied by modifying the fine lactose concentration on the surface of the lactose carriers using wet decantation. Methods. Fine lactose was removed from lactose carriers by wet decantation using ethanol saturated with lactose. Particle sizing was(More)
The study investigated the role of agglomeration and the effect of fine lactose size on the dispersion of salmeterol xinafoate (SX) from SX–lactose mixtures for inhalation. Particle size distributions were characterised by Malvern Mastersizer S, Aerosizer and Spraytec, and imaging conducted by scanning electron microscopy (SEM). Inter-particulate adhesion(More)
The effect of concentration and particle size on the adhesive tendency of drug particles in a model interactive system was investigated using a centrifuge technique. The model interactive system consisted of drug powders adhered to coated glass carrier beads. Adhesion profiles of per cent of drug remaining on the carrier versus the square of the speed of(More)
The influence of relative humidity on the adhesive properties of model drug-carrier interactive systems was investigated using the centrifuge method. The degree of adhesion was quantified by determining the S50 from the adhesion profile. High ambient humidity (greater than 40% r.h.) decreased the degree of interaction of three sulphonamide powders with(More)
The in vitro dispersion of salmeterol xinafoate (SX) alone and four SX (2.5%)-coarse lactose (CL) mixtures containing 0%, 5%, 10% and 20% micronised lactose (ML) was monitored during 18-month storage at 33%, 55% and 75% relative humidity (RH) using a twin stage impinger. The surface moisture was monitored over 2 months by thermo gravimetric analysis. The(More)
The objective was to understand the mechanism of enhancement in salbutamol sulphate (SS) respiratory deposition through addition of magnesium stearate (MgSt). The mixing of MgSt with micronized SS occurred using a Turbula mixer (101 rpm), whilst varying mixing time and MgSt concentration and size. Deposition of SS was determined by a twin-stage impinger.(More)
The purpose was to calculate distributions of powder strength of a cohesive bed to explain the de-agglomeration of lactose. De-agglomeration profiles of Lactohale 300® (L300) and micronized lactose (ML) were constructed by particle sizing aerosolised plumes dispersed at air flow rates of 30–180 l/min. The work of cohesion distribution was determined by(More)
This study investigated the relationship between surface energy of micronized lactose, coarse lactose and salmeterol xinafoate and dispersibility from a mixture after storage at 75% RH. Surface energies, dispersibility, morphology, and the presence of amorphous domains were determined by inverse gas chromatography, twin stage impinger, scanning electron(More)