Dry powder inhalation: past, present and future

ABSTRACT

Introduction: Early dry powder inhalers (DPIs) were designed for low drug doses in asthma and COPD therapy. Nearly all concepts contained carrier-based formulations and lacked efficient dispersion principles. Therefore, particle engineering and powder processing are increasingly applied to achieve acceptable lung deposition with these poorly designed inhalers.

Areas covered: The consequences of the choices made for early DPI development with respect of efficacy, production costs and safety and the tremendous amount of energy put into understanding and controlling the dispersion performance of adhesive mixtures are discussed. Also newly developed particle manufacturing and powder formulation processes are presented as well as the challenges, objectives, and new tools available for future DPI design.

Expert opinion: Improved inhaler design is desired to make DPIs for future applications cost-effective and safe. With an increasing interest in high dose drug delivery, vaccination and systemic delivery via the lungs, innovative formulation technologies alone may not be sufficient. Safety is served by increasing patient adherence to the therapy, minimizing the use of unnecessary excipients and designing simple and self-intuitive inhalers, which give good feedback to the patient about the inhalation maneuver. For some applications, like vaccination and delivery of hygroscopic formulations, disposable inhalers may be preferred.

KEYWORDS:

• Adhesive mixtures
• dry powder inhaler design
• drug formulation
• drug deposition
• inhalation
• particle engineering

Article highlights

• Early dry powder inhalers have a poor drug delivery performance due to design weaknesses

• Formulation studies currently outnumber device design and development studies and are meant to make old inhaler concepts perform better

• Large amounts of excipients in high dose formulations are unwanted: they increase the number of inhalations of a single dose, whereas their safety in the long term is uncertain

• New applications, particularly pulmonary vaccination, require more effective inhalers

• Future inhalers have to be simple (but effective) and give good feedback to the patient to increase adherence to the therapy

• Several applications (e.g. delivery of hygroscopic drug formulations and vaccination) are served better with disposable inhalers

This box summarizes key points contained in the article.

Declaration of interest

The contents of this article is the authors’ responsibility and neither COST nor any person acting on its behalf is responsible for the use which might be made of the information contained in it. AH de Boer, P Hagedoorn and HW Frijlink receive royalties from the Novolizer and Genuair sales and are involved in the development and production of the Twincer platform by pureIMS. F Grasmeijer and M Hoppentocht are part-time employees of pureIMS and F Buttini receives research grants from Chiesi Pharmaceutici SpA, Qualicaps® Europe S.A.U. and Plastiape SpA for inhalation projects. The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

The authors would like to acknowledge the financial support provided by COST- European Cooperation in Science and Technology, to the COST Action MP1404: Simulation and pharmaceutical technologies for advanced patient tailored inhaled medicines (SimInhale).