AMBULATORY INHALATION-THERAPY IN OBSTRUCTIVE LUNG-DISEASES

The inhalation route is widely used for the treatment of obstructive l ung diseases, because administered drugs have a high therapeutic index as they reach their target directly; this requires that they be of ad equate size to penetrate the conducting airways, i.e. 2-5 mu m. Pressu rized inhalers were the first reliable metered-dose devices available, and are still the most frequently used. However, metered-dose inhaler (MDI) suspensions will have to be reformulated: they contain chlorofl uorocarbons (CFCs), whose production has to be stopped within a few ye ars, as they affect the stratosphere. Another limitation of MDI usage is paradoxical bronchospasm; this phenomenon, however, occurs in a low number of patients and is rarely clinically relevant. The main cause of concern with MDIs is their misuse by more than 50% of patients, whi ch leads to a reduced lung deposition and clinical efficacy. Therefore , other inhalation devices have been developed: spacers, dry-powder in halers (DPIs), and breath-actuated MDIs have been shown to increase lu ng deposition of drugs in poor coordinators. However, all have limitat ions which may have varying consequences on clinical efficacy: cumbers ome dimensions of spacers, effect of inspiratory flow rate and humidit y on lung deposition of dry powders, need for reformulation with CFC-f ree gases for breath-actuated pressurized inhalers. Reformulation of M DI aerosols is a complex procedure, which may not be feasible for all drugs. The new products need extensive toxicological and clinical test ing, as some of their characteristics may differ from those of their p redecessors.