Cookie policy: This site uses cookies (small files stored on your computer) to simplify and improve your experience of this website. Cookies are small text files stored on the device you are using to access this website. For more information please take a look at our terms and conditions. Some parts of the site may not work properly if you choose not to accept cookies.


Subscribe or Register

Existing user? Login

Respiratory tract diseases

Blue, brown and now green

The ‘NHS long-term plan’ has called for a shift towards inhalers with a lower carbon footprint.

386 387 Infographic

Source: Astrazeneca; Javier Trigo; Mclean

Download the full print version of the infographic here.

Timeline Innovation in inhaler design

Timeline: Innovation in inhaler design

Source: Mclean





What are the main differences between inhalers?

In adults, there is no difference in clinical effectiveness between a metered-dose inhaler (MDI) with a spacer and a dry powder inhaler (DPI) or soft-mist inhaler (SMI). The most important factor in choosing a device is whether the patient can use it effectively and is happy to do so, followed by cost and environmental impact.


Metered-dose inhalers

  • Design: Pressurised canister containing drug, propellants, surfactants, preservatives, and flavouring agents, released through a metering valve and stem when actuated. Can also be breath-actuated. 
  • Technique: Slow, steady inhalation. 
  • Advantages: Portable and compact; quick to use; over 100 doses; no contamination of contents; high-dose reproducibility; relatively cheap. 
  • Disadvantages: Contain propellants; coordination of breathing and actuation needed (if not a breath-actuated device); low lung deposition (10–20%); upper limit to unit dose content; number of remaining doses is difficult to determine; potential for abuse; not all medicines available. 
  • CO2equivalent: High (approximately 10–25kg per inhaler [e.g. generic salbutamol, Salamol, AirSalb, Clenil, QVAR, generic beclomethasone, Seretide Evohaler, Fostair, Sirdupla, AirFluSal, Serevent Evohaler and generic salmeterol]) to very high (approximately 25kg per inhaler or more [e.g. Ventolin Evohaler, Flutiform and Symbicort]).

Soft-mist inhalers

  • Design: An extremely fine nozzle atomises the drug solution using mechanical energy imparted by a spring, producing a fine, slow-moving mist.
  • Technique: Slow, steady inhalation.
  • Advantages: Propellant not required; compact and portable; multi-dose device; high lung deposition (>50%).
  • Disadvantages: Only two medicines available; some coordination of actuation and breathing required; some patients may find loading difficult.
  • CO2equivalent: Low (approximately 1kg per inhaler).

Dry powder inhalers

  • Design: Inhalation creates turbulent pressure that deaggregates the drug from the excipient in the dry powder formulation. The clinically effective inspiratory flow rate (IFR) for all DPIs is 30–90L/min, but the IFR for optimal delivery varies depending on the device’s resistance.
  • Technique: Quick, deep inhalation.
  • Advantages: Coordination between actuation and breathing is not required; propellant not required; small and portable; quick to use; higher lung deposition than MDIs (15–40%); dose counters in most newer designs. 
  • Disadvantages: May require moderate to high inspiratory flow; some units are single dose; can result in high pharyngeal deposition; not all medicines available. 
  • CO2 equivalent: Low (approximately 1kg per inhaler).

Reducing the environmental impact 2

Source: Mclean


Citation: The Pharmaceutical Journal DOI: 10.1211/PJ.2020.20208093

Have your say

For commenting, please login or register as a user and agree to our Community Guidelines. You will be re-directed back to this page where you will have the ability to comment.

Recommended from Pharmaceutical Press

  • Print
  • Share
  • Comment
  • Save
  • Print Friendly Version of this pagePrint Get a PDF version of this webpagePDF

Supplementary information

Newsletter Sign-up

Want to keep up with the latest news, comment and CPD articles in pharmacy and science? Subscribe to our free alerts.