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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5593_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter Thirty-Seven
Inhaled route
Peter M. Richards
37
STUDY POINTS
*
The rationale for using the inhaled route
*
The appropriate use of the most widely prescribed
inhaled medicines
*
The role of the peak flow meter
*
The different types of inhaler, and inhaler
technique
*
Nebulized therapy
The role of the pharmacist
Inhaled products are specialized dosage forms, which
are designed to deliver medicines directly to the lung.
A variety of inhaler devices are in use, all of which
require the user of the inhaler to adopt an appropriate
inhaler technique. Failure to use the correct inhaler
technique will result in treatment failure. The pharmacist, who is usually the person who gives (dispenses) the inhaler to the patient, is ideally placed
to demonstrate the appropriate inhalation technique
for that inhaler. Using an inhaler is a skill subject to the
development of ‘bad habits’ which can lead to poor
technique. Inhaler technique should therefore be regularly checked to ensure that the technique is optimal; again the pharmacist is ideally placed to perform
this function.
Pharmacists can also provide education to patients
beyond a discussion of a patient’s inhalers and other
medicines, to include education about the patient’s
disease (e.g. asthma) and its management. Pharmacists
also run asthma clinics and may do so as supplementary
or independent prescribers. A few pharmacists have
specialist respiratory consultant posts in secondary
care. A pharmacist wishing to undertake a specialist
role in respiratory medicine will need to gain appropriate experience and undertake further training
such as that offered by the National Respiratory
Training Centre, Warwick.
This chapter describes the most frequently prescribed inhaled therapies in the context of asthma
and chronic obstructive pulmonary disease (COPD).
The most widely prescribed inhaler devices are outlined along with instructions in their use.
Introduction
Many patients on inhaled therapy will be using
more than one inhaler and may also have been
prescribed a peak flow meter (PFM) to aid in monitoring their condition. In order for pharmacists to
be able to provide useful education and advice to
these patients, pharmacists will need to understand
the condition being treated and the role of the
medicines and devices prescribed. This chapter will
provide that understanding in the context of the
two most common airways diseases treated with
inhaled medicines, namely asthma and COPD. It
is beyond the scope of the chapter to discuss the
diseases themselves, or the role of oral therapy and
non-drug management of these conditions (see
Clinical Pharmacy and Therapeutics, Walker &
Whittlesea 2007). It should be remembered that
the most important intervention in COPD is smoking
cessation, and that oral steroids can be life-saving in
acute severe asthma.
There are significant differences in the way that
inhalers are prescribed for asthma and COPD. In
SECTION FOUR Dispensing and related pharmaceutical practice activities
COPD the emphasis of treatment is on the use of
bronchodilators, and it may be appropriate for a
COPD patient to have a long-acting inhaled betaagonist without an inhaled steroid. This is different
from asthma treatment where a long-acting betaagonist should always be prescribed with an inhaled
steroid. The scope of this chapter is limited to commonly used inhaled treatments and devices used for
these inhaled treatments. By being familiar with national treatment guidelines for asthma and COPD, pharmacists can be assured that the advice that they give
patients is likely to be consistent with that given by
other healthcare professionals. These guidelines are
widely available, e.g. in the British National Formu-
lary (BNF) or at http://www.sign.ac.uk/guidelines/
and click on ‘By subject’ then ‘Respiratory Medicine’
for asthma guidelines, and http://guidance.nice.org.
uk/cg12 for COPD guidelines.
Asthma is a very common condition in the UK,
affecting at least 5% of adults and up to 20% of children. It is therefore likely that 1 in 5 of the population
will experience symptoms attributable to asthma at
some time in their life.
COPD has been an under-publicized condition.
Prevalence in 40–70-year-olds in the USA is estimated at around 10% and prevalence is likely to be similar
in the UK. The decline in lung function leading to
COPD is age related but this decline can be rapidly
accelerated in some smokers. COPD is thus an increasing problem in an ageing population.
Asthma and COPD are not mutually exclusive and
some patients will have features of both diseases; this
is often referred to as ‘mixed disease’.
The prevalence of asthma, COPD and related conditions means that pharmacists will not only frequently be encountering patients on inhaled therapy during
dispensing, but will also encounter patients on inhaled
therapy when giving advice on the sale of over the
counter medicines. This chapter not only provides
pharmacists with the knowledge to confidently discuss with patients their use of inhaled therapy but also
to be aware of some signs and symptoms that may be
associated with poor disease control.
The inhaled route
The inhaled route delivers medicines to the lungs.
Inhaled medicines may have a local effect on the
lungs, or may be absorbed to give a systemic effect.
The inhaled route is generally used when the lung is
the target organ, e.g.:
*
The antibiotic colistin is nebulized to treat lung
infections associated with cystic fibrosis
*
The antiviral zanamivir is presented as a
dry-powder inhaler for treating influenza.
Using the inhaled route when the lung is the target
organ has a number of advantages:
*
A smaller dose can be used. The normal adult oral
dose of salbutamol is 4 mg, but the normal inhaled
dose of salbutamol is 200 micrograms (0.2 mg)
*
The risk of unwanted systemic effects is reduced
*
A faster onset of action may be achieved with some
drugs, e.g. salbutamol
*
Topically active drugs with poor oral bioavailability
can be used.
The main disadvantage of the inhaled route is that
inhaling a drug is more difficult than swallowing a
tablet. Some drugs are ineffective by the inhaled
route, e.g. theophylline.
Using the inhaled route does not result in the
entire quantity of drug in the inhaler device reaching
the lung. Even if an inhaler device is used perfectly, it
Figure 37.1*Airways obstruction in asthma. (A) Unobstructed airway. (B) Obstructed airway.
400
is unlikely that any more than 20% of the drug reaches
the lung. The majority of the rest of the drug remains
in the oropharynx and is normally swallowed.
The lungs are designed to prevent the inhalation of
anything other than gas. However, particles with a
diameter of approximately 5 mm can be inhaled and
have sufficient mass to settle in the lung. Particles
larger than 10 mm remain in the oropharynx. Particles
smaller than 1 mm are inhaled, but are then exhaled.
Decreasing particle size increases the chance of penetration further down the tracheobronchial tree. It
may be that a particle needs to be less than 3 mmto
reach the 8th to 23rd branch generation. These
particle sizes apply to the adult lung, and a smaller
particle size of the order of 2.5 mm may be optimal in
infant lungs.
The specific target in the lung for medicines used in
asthma and COPD is the bronchiole. Branching from
bronchi, bronchioles are the first airways in the lung
not to contain cartilage and are less than 1 mm in
diameter. The absence of cartilage means that smooth
muscle contraction reduces the size of the airway.
Inflammation also results in reduction in size of the
airway (Fig. 37.1).
Inhaled route CHAPTER 37
*
Frequent usage of a reliever inhaler may indicate
severe uncontrolled asthma
*
There is no risk that using the reliever inhaler
whenever needed will result in a diminishing
response, but worsening asthma will not respond to
a reliever inhaler alone – additional treatment is
required
*
If the reliever inhaler is not relieving symptoms,
urgent medical attention is required
*
If reliever inhaler usage has increased, or is being
used more than three times a week most weeks,
review of treatment is required
*
The reliever inhaler can be used 15–20 minutes
before sport/exercise to prevent exercise-induced
asthma in susceptible individuals
*
A reliever inhaler is normally blue.
For COPD, a short-acting beta
agonist may be
2
prescribed for regular four times a day use as well as
for symptom relief. In COPD, if a short-acting beta
agonist is not sufficient, the next step may be to add
a short-acting beta
agonist/anticholinergic broncho-
2
dilator.
Unwanted effects of inhaled beta
agonists are rare
2
but tremor can occur.
2
Inhaled medicines used for asthma and COPD
Short-acting beta2agonists
Salbutamol and terbutaline are short-acting beta2agonists and are the most widely used inhaled bronchodilators. They act on beta
muscle of bronchioles to reverse bronchospasm. The
latter can cause symptoms including wheeze, coughing, breathlessness and a feeling of tightness of the
chest. For this reason, short-acting beta
often referred to as ‘relievers’ and should be used ‘as
required’ to relieve symptoms. If a reliever inhaler is
required for asthma more than three times a week
most weeks, the addition of a ‘preventer’ (usually a
steroid) inhaler should be considered.
Points to note
*
The inhaler itself is not dangerous – but asthma is
potentially life-threatening
*
Appropriate, ‘as required’ use of a reliever inhaler
provides a useful marker of the severity of the
condition
receptors in the smooth
2
agonists are
2
Short-acting anticholinergics
(antimuscarinics)
The most commonly prescribed short-acting anticholinergic bronchodilator is ipratropium. Smooth
muscle relaxation is achieved by opposing the parasympathetic nervous system. Ipratropium requires
four times daily inhalation, and is more commonly
used in patients with COPD than in asthmatics.
Long-acting beta2agonists
Salmeterol and formoterol are inhaled long-acting
agonist bronchodilators. They are normally used
beta
2
twice daily, and are indicated for people with asthma
who are symptomatic despite adequate doses of
inhaled steroids. Formoterol is also licensed for
once-daily use. These inhalers are sometimes referred
to as ‘protectors’.
Points to note
*
Protector inhalers should be used regularly and not
on an ‘as required’ basis
401
SECTION FOUR Dispensing and related pharmaceutical practice activities
*
A reliever inhaler (short-acting beta2agonist)
should be used to relieve breakthrough
symptoms
*
Inhaled steroids (preventer inhalers) should be
The above measures form the basis for assessing control of asthma; in addition, limitation of exercise due
to asthma and measures of lung function can be considered.
continued.
For COPD, a long-acting bronchodilator (beta
nist or anticholinergic) is the next step to short-acting
bronchodilators (beta
A short-acting beta
agonist and anticholinergic).
2
agonist will also be required to
2
relieve breakthrough symptoms.
Long-acting anticholinergics
2
ago-
Points to note
*
*
*
Inhaled steroids should be used regularly, not on an
‘as required’ basis
Inhaled steroids have no immediate effect
Improved asthma control will take a minimum of
1–3 days, and it may be 14–28 days before
maximum improvement is seen after starting or
increasing the dose of inhaled steroid
Tiotropium is a once-a-day inhaled anticholinergic
indicated as regular preventative therapy for COPD.
*
Steroid inhalers are normally brown, orange or
maroon.
Unwanted systemic effects of inhaled steroids are
Inhaled steroids
The powerful anti-inflammatory actions of steroids
ideally suit them to control the inflammatory processes in asthma.
The inhaled route allows small doses of steroid to
extremely rare provided that the total daily dose is
less than the equivalent of 800–1000 micrograms
beclometasone diproprionate.
Unwanted local effects of inhaled steroids are:
*
Oral candidiasis (thrush)
*
Dysphonia.
be used, minimizing the risk of systemic effects. The
ideal inhaled steroid’s properties would include:
*
Poor absorption from the gastrointestinal tract to
minimize systemic effects due to the swallowed
Combination long-acting beta
agonist/steroid inhalers
portion
*
Almost complete metabolism in the ‘first pass’
through the liver
*
High topical activity
*
Metabolism in the lung to inactive metabolites
(absorption from the lung circumvents the ‘first
pass’ through the liver).
Using a spacer device with the steroid inhaler, and/or
rinsing the mouth with water and spitting immediately after using the inhaled steroid may further reduce
systemic effects.
Beclometasone, budesonide and fluticasone are
examples of inhaled steroids. They are normally used
twice daily. Budesonide is also licensed for once-daily
use. Ciclesonide is a recently introduced inhaled steroid licensed for once-a-day use. Inhaled steroids are
often referred to as ‘preventers’.
Inhaled steroids should normally be introduced:
*
After a severe exacerbation of asthma
*
If an asthmatic is using his short-acting beta
2
agonist more than three times a week
*
If asthma is causing waking one night a week or
more.
Salmeterol is combined with fluticasone in three different strength combinations as an aerosol metered
dose inhaler (MDI) and in three different strength
combinations as a dry powder inhaler (DPI). Formoterol and budesonide are combined in three different
strength combinations as a dry powder inhaler. These
inhalers are convenient for patients who require both
an inhaled steroid and a long-acting beta
In general these combination inhalers are used as
regular preventative therapy with the dose adjusted to
achieve long-term control of asthma; a short-acting
beta agonist inhaler being used for control of breakthrough symptoms. However, a budesonide 200
microgram/formoterol 6 microgram dry powder inhaler has recently been granted a license for preventer
(maintenance) and reliever use for asthma. Thus
some asthmatics who are using a budesonide 200
microgram/formoterol 6 microgram inhaler may
only need to have one inhaler. A budesonide 200
microgram/formoterol 6 microgram inhaler can only
be used for relief of symptoms if also being used
as a regular preventer. It is not licensed for use before exercise to prevent exercise-induced asthma; an
agonist.
2
2
402
additional short-acting beta2agonist should be used
for this purpose.
Fluticasone 500 microgram/salmeterol 50 microgram dry powder inhaler and budesonide 400 microgram/formoterol 12 microgram dry powder inhaler,
twice daily, are licensed for certain patients with
COPD. That is for those whose forced expiratory
volume in 1 second (FEV
) is less than 50% predicted
1
and who are frequent exacerbators (two or more
exacerbations per year).
The peak flow meter
The peak flow meter (PFM) is a simple inexpensive
device, prescribable on the NHS, which gives a useful
objective measure of airways obstruction. A peak flow
meter and its correct use is illustrated in Figure 37.2.
The PFM measures peak expiratory flow rate (PEFR).
PEFR is expressed in litres per minute (L/min). Flow
rate of gas through a tube is proportional to the diameter of the tube when the pressure exerted on the gas
is constant. Thus the maximum rate at which individuals can expel air from their lungs is proportional to
the patency of the tubes in their lungs. A reduced
PEFR indicates that there is obstruction to airflow
in the lungs.
Asthmatics will obtain useful information about
their condition by using the PFM twice daily and
charting their results for 2–4 weeks in the following
situations:
*
To confirm a diagnosis of asthma (a diurnal
variation of PEFR of more than 20% is
characteristic of asthma)
Inhaled route CHAPTER 37
*
To establish the level of control of asthma on
current therapy
*
To track improvement of control of asthma
following the introduction of a new treatment
*
To ensure asthma control is maintained when
treatment is stepped down
*
As an aid to self-management of asthma.
Normal values are available for PEFR in graph or chart
form or on ‘wheels’. In adults, normal values for PEFR
vary by age, sex and height; for children, PEFR varies
justbyheight.NormaloraveragevaluesofPEFRarejust
that and values of 50–100 L/min above or below a predictedvaluefall within the normalrange.An increase of
at least 20% in PEFR following the use of an inhaled
short-actingbeta
agonistsuchas salbutamol is diagnos-
2
tic of asthma. This is known as a reversibility test.
The PFM is of less value in COPD as the airways
obstruction tends to be fixed rather than variable, and
lung volumes may be more important. Spirometry,
which measures FEV
and forced vital capacity
1
(FVC) is a more useful test of lung function in COPD.
Types of inhaler device
Aerosol inhalers
Metered dose inhaler (MDI)
An MDI (Fig. 37.3) delivers an aerosol of drug dissolved or suspended in a propellant. Immediately an
MDI is actuated, some of the propellant rapidly evaporates to produce droplets of appropriate size to be
inhaled into the lung. Further evaporation of propellant may occur in the mouth and the so-called
Figure 37.2*The correct use of a peak flow meter (PFM).
Figure 37.3*The main elements of a metered dose inhaler.
403
SECTION FOUR Dispensing and related pharmaceutical practice activities
‘cold-freon effect’ occurs if there is further evaporation of propellant (freon) when the aerosol impacts on
the back of the throat. The sensation produced by the
cold-freon effect can be sufficient in a minority of
individuals to stop the inhalation and means that these
individuals cannot use MDIs. The propellants currently used are generally hydrofluoro-alkanes (HFAs).
Chlorofluoroalkanes, also known as chlorofluorocarbons (CFCs), were formerly used as propellants, but
are now banned by international treaty because of
their ozone-depleting properties. Medical aerosols
were given exemption from the ban on CFCs, until
alternatives were found and tested. Currently the
change from CFCs to HFAs is not complete. It should
perhaps be noted that while HFAs do not have the
ozone-depleting effects of CFCs, both CFCs and
HFAs are ‘greenhouse’ gases.
Patients who have previously had CFC-containing
MDIs may be concerned when they start using a
CFC-free MDI, because the taste and ‘feel’ of the
aerosol is different. These differences are largely due
to the fact that most CFC-containing MDIs are suspensions of drug in propellant, whereas most CFCfree MDIs are solutions of drug in propellant. Suspensions of drug in propellant result in nearly all the
propellant evaporating after actuation and this can
Figure 37.4*How to use a metered dose inhaler. (Source:
National Respiratory Training Centre.)
cause the cold-freon effect (see above). For many
people this cooling sensation provides feedback that
they are inhaling the drug. Solutions of drug in propellant result in only a fraction of the propellant
evaporating after actuation, resulting in a reduced
potential for the cold-freon effect but also a different
‘feel’ for the patient.
Surfactants such as oleic acid and cosolvents such
as ethanol may be used to facilitate the production
of an appropriate suspension or solution of drug in
propellant.
The propellants, which are gases at room temperature, are maintained as liquids by filling under pressure into the metal aerosol canister.
A metered dose is achieved by having an appropriate size reservoir in the valve, which fills by gravity as
the valve re-seats after each actuation.
The correct method of using an MDI is shown in
Figure 37.4.
Common errors in using an MDI include:
*
Inability to coordinate actuation of the inhaler with
inspiration
*
Taking a short, sharp inspiration, instead of a long,
steady inspiration (this is often at least in part due
to not exhaling before using the inhaler)
*
Actuating the inhaler twice (or more) on one
inspiration.
Breath-actuated MDI
Inhaling through a breath-actuated MDI triggers a
mechanism that ‘fires’ (actuates) the aerosol. These
inhalers are particularly useful for those patients who
have difficulty coordinating inspiration with actuation
of the MDI.
Easi-Breathe
correct use is shown in Figure 37.5.
Autohaler
an Autohaler
Breathe
raising a lever on the top of the inhaler, whereas the
Easi-Breathe
cover.
Common errors when using a breath-actuated
MDI include:
*
Not achieving a sufficiently high inspiratory flow
rate to actuate the device
*
Stopping inhaling immediately the inhaler
actuates.
is a type of breath-actuated MDI; its
is another breath-actuated MDI. Using
is essentially the same as using an Easi-
except that the Autohaleris primed by
is primed by opening the mouthpiece
404
Inhaled route CHAPTER 37
Figure 37.5*How to use the Easi-Breathe. (Source: National
Respiratory Training Centre.)
MDI + spacer
A chamber device (spacer) may be attached to an
MDI (Fig. 37.6).
A spacer consists of a plastic chamber with a port at
one end for the MDI and in most cases a one-way
valve and mouthpiece at the other end.
An MDI + spacer is best used by firing a single
dose from the MDI; inhalation should then start as
soon as possible.
A spacer may be used with an MDI for the following reasons:
*
To overcome difficulty in coordinating inspiration
with actuation of the MDI, as the inspirable
particles remain available for inhalation for some
seconds after actuation
*
To decrease deposition of non-respirable particles
in the oropharynx. The larger particles are
deposited in the spacer, rather than the
oropharynx. This may be particularly important for
high-dose inhaled steroids
*
To allow those unable to distinguish between
inspiration and expiration (e.g. young children) to
Figure 37.6*How to use a spacer device, e.g. Volumatic.
Method for patients who can use the device without help.
(Source: National Respiratory Training Centre.)
benefit from inhaled therapy by simply inhaling
and exhaling across the one-way valve
*
To deliver a large dose of bronchodilator in an acute
attack. The MDI is ‘fired’ a number of times into
the spacer and the asthmatic inhales the drug by
breathing through the one-way valve.
A mask may be attached or be integral to a spacer.
The mask can then be placed over the mouth and
nose of babies or infants to enable them to benefit
from inhaled therapy. The correct use of a spacer and
facemask is shown in Figure 37.7.
Examples of spacers are Volumatic
, Nebuhaler
and Aerochamber.
Dry powder inhaler (DPI)
Medicines for inhalation can be presented as a micronized powder. The powder may be pure drug as in the
Turbohaler
lactose, as in Rotacaps
When a carrier powder is used, the drug particles
are adhered by weak electrostatic forces to the much
larger carrier particles. As the drug/carrier powder is
, or be drug and a carrier powder such as
, Diskhalerand Accuhaler.
405
SECTION FOUR Dispensing and related pharmaceutical practice activities
Figure 37.7*How to use a large-volume spacer and face
mask. (Source: National Respiratory Training Centre.)
inhaled from the inhaler, the small respirable drug particles fly off the larger non-respirable carrier particles.
The lactosecarrier thusremains in the mouth. Patients
using DPIs that employ a carrier powder should be
reassured that even when using the inhaler correctly
they will have carrier powder left in the mouth.
Patients inhaling pure drug from a Turbohaler
may experience little or no taste.
The correct method of using the Turbohaler
shown in Figure 37.8 and the Accuhaler
Figure 37.9.
All inhalers are boxed with instruction leaflets.
However, the best way to learn how to use an inhaler
is to have the technique demonstrated, then to
Figure 37.8*How to use the Turbohaler. (Source: National
Respiratory Training Centre.)
is
in
Figure 37.9*How to use the Accuhaler. (Source: National
Respiratory Training Centre.)
406
Inhaled route CHAPTER 37
Table 37.1 Differences in the use and care of metered dose inhalers and dry powder inhalers
MDI DPI
Coordination of actuation and inhalation required No coordination required as the release of
powder and inhalation is a two-step process
Long, slow inhalation is the ideal to allow vaporization of propellants Inhalation should be vigorous to disperse drug particles
Should be washed at least once a week to prevent blockage of actuator Inhalers containing drug, e.g. Turbohaler
must never be washed. Inhalers that do not contain
drug, e.g. Rotahaler
completely dry before use
Exhalation prior to inhalation can be into the inhaler Exhalation must never be into the inhaler
, may be washed but must be
,
attempt to use the inhaler under supervision so that
any errors can be corrected. Many patients will benefit from pharmacists providing this service. Similarly,
for pharmacists to best learn how to provide this service, they too should be shown how to use the inhaler
and how to spot common errors. Medical representatives from companies that market inhalers are usually
more than happy to train pharmacists how to use,
demonstrate and check inhaler technique. As part of
this service, the medical representative will provide
placebo inhalers, to allow the pharmacist to demonstrate the correct inhaler technique, instruction leaflets and other patient education material.
The use and care of a DPI differs from that of an
MDI, as shown in Table 37.1.
Nebulizers
Medicines for inhalation can be presented as solutions
or suspensions for nebulization. A nebulizing system
(Fig. 37.10) usually consists of a compressor supplying compressed air to a nebulizing chamber, which
delivers the nebulized drug to the patient via a mouthpiece or face mask. The face mask is most commonly
used but when deposition of the nebulized drug on
the face is undesirable (e.g. a steroid), then a mouthpiece is preferable, or the face under the mask should
be protected with petroleum jelly.
The principle of jet nebulization is shown in
Figure 37.11. The gas used to drive the nebulization
process may be oxygen or air, but in either case a
minimum flow rate of 8 L/min at a pressure of at least
69 kPa (10 psi) is required.
Patients using more than one nebulized medicine
may have two different solutions mixed in the nebulizing chamber to be nebulized together. The Sum-
mary of Product Characteristics (SPC) may give
advice on other solutions and diluents that may be
appropriately mixed with a given medicine for nebulization. It is possible that one solution will precipitate the other; this can normally be detected by the
mixed solutions in the nebulizer changing from clear
to cloudy. Such a change means that the mixed
solutions are not compatible and should not be nebulized together. Consideration should also be given
to the total volume of the mixed solutions, as
the larger the volume, the longer it will take to be
nebulized.
Nebulizers are used when high doses of drug are
required and/or when the patient is unable to use any
form of inhaler. Nebulizers do not require the patient
to learn any technique and are effective on normal or
shallow breathing.
Nebulizers are used in the treatment of severe
acute asthma and this is best done under medical
supervision:
*
To ensure that an adequate objective and
maintained response to treatment is achieved
(e.g. by measuring PEFR before and after
nebulization)
*
To assess if other treatment is indicated, e.g. oral or
parenteral steroids
*
To plan follow-up and possible review of chronic
medication.
Nebulized treatment may also be used in the latter
stages of COPD often in conjunction with domiciliary
oxygen therapy. Domiciliary oxygen cylinders do not
provide sufficient flow rates to produce adequate
nebulization, so a compressor unit should be used.
Drugs for nebulization are normally presented as
unit dose vials; examples of these are Nebules
Respules
.
and
407
SECTION FOUR Dispensing and related pharmaceutical practice activities
Figure 37.10*Nebulization equipment.
classes of drugs: inhaled bronchodilators and
inhaled steroids
*
Inhaled bronchodilators can be further subdivided
into beta
agonists and anticholinergics
2
(antimuscarinics). Each of these classes can be
further subdivided into short acting and long acting
*
National and international management guidelines
are available for asthma and COPD and treatment
is based on a step-wise approach
*
A range of inhalation devices is available to deliver
drugs directly to the lungs. This has clear
advantages including using much lower doses
compared to oral therapy
*
The use of inhalers is technique dependent and
patients require training in their use
*
Medicines to be inhaled are presented as aerosol
inhalers, dry powder inhalers or liquids to be
nebulized
*
The most widely prescribed inhaler device is the
aerosol metered dose inhaler (MDI). The MDI may
be used in conjunction with a spacing device (a
‘spacer’). A modified form of the MDI, triggered to
actuate by inhalation, is a breath-actuated MDI.
Both the ‘spacer’ and the breath-actuated MDI
overcome the main difficulty of using an MDI, the
need to coordinate inhalation with actuation of the
Figure 37.11*The principle of jet nebulization.
KEY POINTS
MDI, and allow a wider range of individuals to
successfully use an MDI
*
Dry powder inhalers (DPIs) were originally
developed to overcome the difficulty some patients
have coordinating inhalation with actuation of an
*
Asthma and COPD are common conditions,
treatment of which is largely dependent on the
inhaled route
*
The vast majority of inhaled treatments for asthma
and COPD can be divided into two pharmacological
MDI
*
DPIs vary widely in appearance and the method by
which the powder is made available for inhalation,
but all rely on inhalation to mobilize the powder
from the inhaler and through the mouthpiece
408