If patients are unable to use their inhaler, drug delivery may be unsatisfactory and the patients may fail to benefit from the prescribed medication. It is important to consider whether patients can use all dry powder inhalers equally well. Changing a patient from a dry powder inhaler used well to one that the patient is unable to operate effectively could compromise asthma control.
The many marketed dry powder inhalers reflect differences in design decisions that could affect lung deposition. Studies using different dry powder inhalers have confirmed that different lung deposition patterns are observed. Furthermore, there may be considerable individual variability in lung deposition. Differences in lung deposition patterns could have clinical effects. Studies may show similar clinical effectiveness with two inhalers, because most products are used at the plateau phase of the dose–response curve, although there may be differences in the adverse event profile.
The ideal inhaler does not yet exist. Different dry powder inhalers show some but not all features of the ideal inhaler; hence, patients may prefer some aspects of one inhaler while favouring a different inhaler for other features. The individual balance of features will govern the overall preference for one inhaler over others.
The method for operation of dry powder inhalers varies. Ease of use is seen as an important consideration when selecting an inhaler device, which should be evaluated in real-life studies using unselected patient populations.
In conclusion, the evidence suggests that patients cannot use all dry powder inhalers equally well.