Michael J. Tobyn

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The mechanical properties of compacts of unlubricated microcrystalline cellulose and silicified microcrystalline cellulose were evaluated using the diametric tensile test. The results suggested that, under comparable testing conditions, compacts of silicified microcrystalline cellulose exhibited greater strength than those of microcrystalline cellulose. In(More)
Atomic force microscopy (AFM) was used to investigate drug-carrier interactions between beclometasone dipropionate (BDP) and a series of untreated and modified lactose surfaces. This quantitative information was correlated with bulk characterization methods and an in-vitro study. Modified lactose surfaces were prepared using a proprietary process referred(More)
When considering the development of potential controlled-release pulmonary drug delivery systems, there is at present no standard method available for the assessment of in vitro drug release profiles necessary to understand how the drug might release following deposition in the lungs. For this purpose, the twin-stage impinger (TSI), apparatus A of the BP,(More)
Surface energy data for samples of microcrystalline cellulose have been obtained using two techniques: capillary intrusion and inverse gas chromatography. Ten microcrystalline cellulose materials, studied using capillary intrusion, showed significant differences in the measured surface energetics (in terms of total surface energy and the acid–base(More)
The adsorption of a model amine drug (tacrine hydrochloride) from aqueous solution onto 21 microcrystalline cellulose (MCC) based samples has been investigated. The MCC source (manufacturer) affected adsorption. The adsorption appeared to be fully reversible. Adsorption was reduced by the use of high-density grade MCC, high-energy milling, and(More)
The atomic force microscope (AFM) has been used to characterize the cohesive nature of a micronized pharmaceutical powder used for inhalation therapy. Salbutamol sulfate (also referred to as albuterol sulfate), a therapeutic drug commonly delivered from dry powder inhalers (DPI), was chosen as a model system because the cohesion and subsequent(More)
The influence of relative humidity (RH) on the cohesion properties of three drugs: salbutamol sulphate (SS), triamcinolone acetonide (TAA), and disodium cromoglycate (DSCG) was investigated using the atomic force microscope (AFM) colloidal probe technique. Micronized drug particles were mounted in heat-sensitive epoxy resin for immobilization. Multiple AFM(More)
The atomic force microscope (AFM) colloid probe technique was utilized to measure cohesion forces (separation energy) between three drug systems as a function of relative humidity (RH). The subsequent data was correlated with in vitro aerosolization data collected over the same RH range. Three drug-only systems were chosen for study; salbutamol sulphate(More)
The surface morphology of α-lactose monohydrate particles was modified by a new wet-smoothing process performed in a high-shear mixer using solvents. Successive steps of wetting and drying of lactose powders during rolling in the mixer's cylindrical bowl were performed. Smoothed particles were tested for size distribution, flow, and packing. The(More)
The variation of aerosolization with humidity for three micronized drugs used in the treatment of asthma was evaluated by using in vitro methods. Micronized samples of disodium cromoglycate (DSCG), salbutamol sulphate, and triamcinolone acetonide (TAA) were stored for 12hr at 15, 30, 45, 60, and 75% relative humidity (RH). A suitable "reservoir" dry powder(More)