Successful use of DPI systems in asthmatic patients—key parameters

Abstract

Effective inhalation therapy using pressurised metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) is the cornerstone of asthma management. Previous studies have demonstrated difficulties in the usage of pMDIs in certain patient groups, especially as pMDis require the co-ordination of inhaler activation with dose inhalation. Almost all DPIs are breath-activated and preclude the need to co-ordinate activation with inspiration. Three key parameters for successful inhaler use should be considered when evaluating existing or future DPI devices: (1) compliance; (2) fine particle distribution and dependency on inspiratory flow and; (3) clinical efficacy. A threshold mechanism which controls for a minimal inspiratory flow rate is desirable in order to support formation of an optimal fine particle fraction (FPF) which in turn improves lung deposition. Additionally, in order to enhance patient compliance an optimal multidose DPI should feature a visual or acoustic feedback of a correct inhalation. The Novolizer is a multidose refillable DPI. It has multiple feedback mechanisms and a trigger flow valve system, which helps to ensure correct inhalation that allows adequate lung deposition, helps to reassure the patient that medication has been taken and might therefore improve patient compliance. The low-to-medium airflow resistance translates into higher peak inspiratory flow (PIF) and makes the Novolizer DPI particularly suitable for the use in patients with reduced inspiratory flow rates. Clinical studies have shown that children, elderly patients, adults with moderate-to-severe asthma and COPD patients (stage IIa-III) are able to generate sufficient inspiratory flow to operate the Novolizer effectively. In contrast previous studies with other MDPIs (e.g. Turbuhaler or Aerolizer) demonstrated that in patient groups with severe obstructive lung disease or in children with asthma optimal inspiratory flow rates are not achieved in all patients.