Abstract

The main inhalation devices widely used today are metered-dose inhalers (MDI), dry powder inhalers (DPI's) and nebulizers. The inhalation therapy has advantages of allowing lower dosage administration, having less side effects and providing more rapid relief of symptoms. Under best circumstances 15-20% of the aerolized medication reaches the lungs. Particles greater than 10 micron are kept in the upper airways. Particles that have a diameter of approximately 5 micron can be delivered to the bronchi.

The metered-dose inhalers have the advantages of the MDIÕs. They can be used rapidly, carried easily, multidosaged and are less expensive than the other devices. Requirement of propellants (chlorofluorocarbon: CFC), large amounts of the oropharyngeal deposition and need for hand -and- mouth coordination are the disadvantages. ÔSpacersÕ are helpful in minimizing the complications and failures related to MDI usage.

The Montreal Protocol has stopped the productions of CFCÕs that are harmful to ozone. The CFC's in the MDI's have been regarded as principle necessities but in the last years hydrofluoroalcanes (HFA) have been proposed as an alternative. With the usage of DPIÕs, double amount of the medication reaches the lungs and the oropharyngeal deposition is less when compared with MDI's. DPI's function with the inspiratory flow and the medication is released automatically. They store very small particles as larger aggregates. The aeresolized particles that are delivered with inspiration have a diameter less than 6 microns. These are called 'small particles'. These are the particles that reach the bronchi and bronchioli. Large sized par - ticles hang in the upper airways. In vitro studies showed that different amounts of small sized particles occur in mild, moderate and strong flow rates. The inner resistance of dry powdered inhaler system does not affect the inspiration rate or small sized particle amount. PatientÕs inspiration rate is a more significant factor. he inspiration rate must be at least 30 l/min. Even patients with severe obstruction can establish inspiration at this rate. The MDI systems currently in use in our country are aeroliser, dischaler, turbuhaler or discus.

The factors affecting the success in inhalation therapy are the patient compliance, the amount deposited in the lungs, inhalation techniques and devices used. In compliance studies, the number of days patients use the proposed drug changed between 20% and 73% during follow-up. Similarly, patients used 63-92% of the prescribed drug dose. Amount of drug deposited in the lungs are affected by inhalation techniques and medical advices. With desired use of the inhalation techniques, the amount of drug deposited may increase to 22.8% from 7.2 %. 90% of patients can make mistakes while using inhalation devices. Uneducated and elderly people make more mistakes. With patient education, the failure rate decreases.