Nycomed Imaging as

Tore Omtveit

Tony Pete

Bjorn Haugseter

Bj&oslash;rn Haugseter

The invention provides a process for the preparation of gas-containing vesicles wherein a mixture of gas, liquid and vesicle membrane forming material is passed through a zone in which it is subject to shear forces exerted by surfaces moving relative to each other at a speed of at least 20 m/s.

Process for preparation of gas containing vesicles

An invention provides a process for the selection from a particulate pharmaceutical product of particles of a preselected size, said process comprising (i) obtaining a substantially homogeneous suspension of said particulate pharmaceutical product in a fluid suspension medium which is immiscible with said product and is of different density to said product, (ii) carrying out a size selection procedure to set an effective lower or upper size limit on the articles in the final particulate product, wherein step (ii) comprises either allowing said suspension to settle for a predetermined period, separating said suspension into a first and second component in a predetermined volume ratio, said first component deriving from an upper layer of said suspension and said second component deriving from a lower layer of said suspension, adding further suspension medium to said first component where said medium is more dense than the pharmaceutical product or to said second component where said medium is less dense than the pharmaceutical product and mixing to produce a substantially homogeneous suspension of particulate pharmaceutical product in said fluid suspension medium, and repeating steps at least once, optionally omitting the last repeat of step whereby to set an effective lower size limit on the particles in the final particulate product, or (viii) allowing said suspension to settle for a predetermined period, (ix) separating said suspension into a third and a fourth component in a second predetermined volume ratio, said third component deriving from an upper layer of said suspension and said fourth component deriving from a lower layer of said suspension, and retaining said third component where said medium is less dense than the pharmaceutical product or said fourth component where said medium is more dense than said product, whereby said second predetermined volume ratio is such as to set an effective upper size limit on the particles in the retained component.

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Oslo, Norway

Tore Omtveit