New developments in inhaler technology can take
8–10 years, and recent approaches have focused on
incorporating the following features: improvement of
aerosol dispersion and production of particles within the
extra-fi ne size range needed for deep lung targeting;
development of methods to reduce eff ort required for
inhalation; and improvement of delivery effi ciency while
maintaining portability and ease of use of the inhaler.
With generic and subsequent market entry products
becoming increasingly available, in-vitro and in-vivo
studies are needed to establish bioequivalence with
trademarked products.6 Some of the regulatory
requirements for generics have changed in recent years,
particularly for DPI generic products. For example, the
appearance of the generic DPI device could be diff erent to
the originally marketed device while necessarily providing
the same dose of drug to the mouth as the original and
also providing aerosol characteristics that are the same.7
Some generic DPIs have diff erent dose strengths and
diff erent numbers of doses to the original. These products
might have obtained approval as new drug products or as
subsequent market entry products; the availability of the
same drug in diff erent formats can lead to confusion for
clinicians prescribing and patients adhering to a treatment
plan. In this Review we highlight new developments in
aerosol technology and novel therapeutic uses that have
emerged in recent years to help improve awareness
among clinicians.
Measuring aerosol drug delivery
The inhaled route can deliver a suffi cient amount of the
drug to airway surfaces throughout the lung to give rise to
a clinical response, although dose delivery is dependent
on the adequate use of an appropriate administered drug
dose and eff ective inhaler use. In patients with airway
narrowing owing to oedema, increased secretions, or
smooth muscle constriction, the distribution of inhaled
aerosol is non-uniform, with increased concentrations
deposited in areas of airway narrowing.8 The amount of
drug available for distribution distal to the obstructed
areas is possibly reduced, which can aff ect clinical
outcomes.9,10 By comparing responses with the same drug
from diff erent delivery systems11 or between diff erent
drugs within the same device category,12 emitted dose or
fi ne particle dose provides a more accurate estimate of the
useful dose available from the inhaler than does the label
claim (fi gures 1 and 2). Because of losses within the
inhaler and on the mouthpiece,15 drug delivery as recorded
by emitted dose is less than that for the nominal dose or
label claim (fi gure 1). Defi ning the unit dose depends on
regulatory practices; nominal dose and label claim are
interchangeable in some countries, whereas the label
claim dose can be less than that for the nominal dose and
equal to that for the emitted dose in other countries.
For example, one of the combination therapies (fl uticasone
propionate/salmeterol) with a dose strength of
125 μg/25 μg in the UK is equivalent to an emitted dose of
115 μg/21 μg in the USA.