The invention provides a pMDI metering valve comprising at least one component which comprises a desiccant-entrained material, a pMDI closed container system containing a desiccant-entrained material, and a method of stabilising the fine particle mass (FPM) of an inhalation drug formulation emitted by a pMDI closed container system comprising providing a desiccant-entrained material inside the pMDI closed container system so as to be in contact with the formulation therein.
