US Patent 9067031 Metered dose valves and dispensers

A metered dose valve for use in a pressurized metered dose dispenser for dispensing a metered dose of an aerosol formulation comprising particles of a medicament suspended in liquefied propellant, optionally in combination with one or more excipients, the valve comprising a metering chamber and at least one porous, fluid permeable, particulate semi-permeable body, the at least one porous body being positioned within a region of the interior conduit of the valve, for example within the metering chamber, or a pre-metering chamber and/or an internal channel upstream of the metering chamber.