Rx Note

Introduction Metered-dose inhalers (MDIs) were introduced in the mid-1950s and are the most commonly used inhalation drug delivery devices. In MDIs, drug is either dissolved or suspended in liquid propellant(s) together with other excipients, including surfactants, and presented in a pressurized canister fitted with a metering valve. Shaking The Canister Pressurized aerosols may be formulated as either solutions or suspensions of drug in the liquefied propellant. In practice, pressurized inhaler formulations have traditionally been almost exclusively suspensions. Hence, all the problems of conventional suspension formulation, such as caking, agglomeration, particle growth, etc. need to be considered. Consequently, suspension-based MDIs should be shaken prior to use , but not the solution-based. Not shaking an MDI canister that has been standing overnight decreases total and respirable dose by 25% and 35% respectively, because the drugs in MDI formulations are usually separated from th...