The present invention provides a metering valve for dispensing a metered dose of product from a canister 2 containing the product and a propellant. In a first embodiment the metering valve body 8 has a propellant metering chamber 26 with a propellant inlet 38 and a product metering chamber 28 with a product inlet 32 as well as a metering valve stem 40 having a dispensing nozzle 42, a propellant inlet plug 54 and a product inlet plug 56. The metering valve stem is movable within the metering valve body to a dispensing position in which the propellant inlet is sealed by the propellant inlet plug and the product inlet is sealed by the product inlet plug and the propellant metering chamber and product metering chamber are in fluid communication with the atmosphere via the dispensing nozzle of the metering valve stem, allowing a metered dose of product and propellant 44 to be dispensed from the metering valve body. In a second embodiment a canister (2, Fig 1) is provided with a high pressure chamber (4, Fig 1) for a liquefied or compressed gas propellant and a low pressure chamber (5, Fig 1) for containing an inhalable drug and a vaporised propellant. A metering valve (8, Fig 1) and pressure regulating valve (12, Fig 1) are interposed between the two chambers for providing a flow path from the high pressure to low pressure chamber when the pressure in the low pressure chamber drops below a predetermined value.
