Inhalation mode of drugs administration provides high concentration of an active substance directly in the respiratory tract and stands for the basic method of treatment of obstructive diseases. There are three main inhaler systems available: pressurized metered-dose inhalers pMDI (used with or without spacers), dry powder inhalers DPI and nubulizers. The choice of appropriate inhaler is crucial in clinical practice and is based on the patients’ preferences, characteristics of the device and the patient knowledge and ability of correct use of the device. The effective lung deposition of inhaled aerosol drugs is related to coordination of inhalation and dose release in pressurized metered-dosed inhalers, to the peak inspiratory flow - PIF  in dry powder inhalers (essential for dose release and cover of resistance given by the device) and to the respiratory cycle (inspiration to expiration ratio) in nebulizers.

At the present time there are new generations of pressurized inhalers available characteristic of increased lung deposition and easier application of the drug. The introduction of hydrofluoroalkanes made a considerable progress in pressurized inhaler technique and aerosol therapy. The use of holding chambers or spacers still remains the method simplifying pressurized inhalers use. Dry powder inhalers are user-friendly. The main differences in dry powder devices characteristics comprise: the flow resistance of the device and the peak inspiratory flow required to lift the powder drug, types of dose counters, the number of available doses (one-dose and multi-dose inhalers) and applied protections against humidity (multi-dose reservoirs and non-reservoir devices).