Key learning points

  • It is important to ensure that patients know how to use their inhalers correctly
  • Inhalers are not the same, nor are they interchangeable
  • There are basically two types of inhaler devices – pressurised metered dose inhalers (pMDIs) and dry powder inhaler devices (DPIs)
  • They contain different medications and doses and have different onsets of action and duration as well as different dosing schedules and uses


Guidelines stress the importance of ensuring that patients can use their inhalers.1,2 This is important in terms of type of inhaler device, purpose, including use and dose, and the ability of the patient to use them. Randomised controlled trials conclude that all inhalers are equivalent,3 but these are within supervised trials with proper instruction. The reality is that there are inferior outcomes for inhaler users due to an inability of healthcare professionals to instruct on correct use and/or an inability of users to use the inhalers correctly.

Types of inhalers

With all the available inhalers currently on the market, it is important that we realise that they are not all the same and that they are certainly not interchangeable. This is for several reasons, the first being the actual device.

There are essentially two types of inhaler devices: pressurised metered dose inhalers (pMDIs), essentially aerosols which also include the soft mist inhaler, and dry powder inhaler devices (DPIs).

With aerosol devices, the ideal inspiratory flow rate is around 30 litres/minute, which is a slow and steady breath in for around 4 seconds.4 The older pMDIs have a low deposition even with an ideal technique, of around 12%,4 although the newer devices have a softer plume and better valve technology, and some have smaller particle size increasing deposition. The Respimat device, although an aerosol inhaler, has a soft mist which increases deposition in the lung.

The DPIs are a dry powder and require less coordination. They do, however, require an adequate inhalation as it is inspiratory flow that releases the medication from the carrier agent. The DPIs require a quick and deep inhalation, which may be problematic in patients with little inspiratory effort, for example those with severely compromised lung function.4

Inhalers contain different medications – bronchodilators or corticosteroids, either singularly or in combination. These have different durations of onset and action and an inhaled corticosteroid, for example, will not give a noticeable effect. As Chrystyn and Price state: if the person does not get instant relief from the inhaler then they may take more doses, or conclude that their inhaler doesn’t work.5

Various inhalers contain different doses of medication, this means they are not interchangeable if consistent dosing is required. Another problem is that some of the generic medications have different equivalent doses to the original inhalers. If patients do not understand that the doses are equivalent they may be reluctant to take doses or feel that they need more than one dose. They also have different durations of action so that some are taken as required, while others have dosing schedules varying from one to three times a day.

Inhaled medications are prescribed for different reasons. Bronchodilators are for relief of bronchoconstriction with some being short acting and not taken on a regular basis, while others are long acting and are taken regularly. Inhaled corticosteroids are for reduction of the inflammatory process in the lung and need to be taken regularly to be effective.

Evidently all inhalers are not the same. Although with many ‘switch’ programmes going on around the country, where one inhaler is changed for another cheaper generic often without any review or guidance to patients, it is not always apparent that this is recognised. We cannot assume that our patient will be able to use a new inhaler device if they receive a prescription and a note on how to do this.

Jane Scullion is a respiratory nurse consultant at the University Hospitals of Leicester.

This project was initiated and funded by Teva Respiratory. Teva have had no influence over content. Topics and content have been selected and written by independent experts.