Inhaled route

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Inhaled route




Study Points



image The rationale for using the inhaled route


image The appropriate use of the most widely prescribed inhaled medicines


image The role of the peak flow meter


image The different types of inhaler, and inhaler technique


image 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.


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. It should be remembered that the most important interventions in COPD are smoking cessation and pulmonary rehabilitation.


There are significant differences in the way that inhalers are prescribed for asthma and COPD. In 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 beta-agonist without an inhaled steroid. This is different from asthma treatment where a long-acting beta-agonist 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: BTS/SIGN Asthma Guideline, 2011 (January 2012 revision): http://www.brit-thoracic.org.uk/guidelines/asthma-guidelines.aspx and NICE CG101 Chronic Obstructive Pulmonary Disease: http://guidance.nice.org.uk/CG101/NICEGuidance/pdf/English.


Asthma is a very common condition in the UK, affecting at least 5% of adults and up to 10% of children; therefore many people will experience symptoms attributable to asthma at some time in their life.


COPD has been an under-publicized condition. Prevalence of COPD in the UK is thought to be 2–4% of the total population with 1.5% of the population with diagnosed COPD. 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 encounter 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.



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.:



Using the inhaled route when the lung is the target organ has a number of advantages:



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 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 μm can be inhaled and have sufficient mass to settle in the lung. Particles larger than 10 μm remain in the oropharynx. Particles smaller than 1 μm 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 μm to 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 μm 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. 43.1).




Inhaled medicines used for asthma and COPD



Short-acting beta2 agonists (SABAs)


Salbutamol and terbutaline are widely used SABAs. They act on beta2 receptors in the smooth muscle of bronchioles to reverse bronchospasm. Symptoms caused by bronchospasm include wheeze, coughing, breathlessness and a feeling of tightness of the chest. For this reason, SABAs are often referred to as ‘relievers’ and should be used ‘as required’ to relieve symptoms. If a reliever inhaler is required for asthma more than twice a week most weeks, the addition of a ‘preventer’ (usually a steroid) inhaler should be considered.



Points to note




image The inhaler itself is not dangerous – but asthma is potentially life-threatening


image Appropriate, ‘as required’ use of a reliever inhaler provides a useful marker of the severity of the condition


image Frequent usage of a reliever inhaler may indicate severe uncontrolled asthma


image 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


image If the reliever inhaler is not relieving symptoms, urgent medical attention is required


image If reliever inhaler usage has increased, or is being used more than twice a week most weeks, review of treatment is required


image The reliever inhaler can be used immediately before sport/exercise to prevent exercise-induced asthma in susceptible individuals


image A reliever inhaler is normally blue.


Unwanted effects of inhaled beta2 agonists are rare but tremor can occur.


SABAs are also prescribed for symptom relief in COPD.




Long-acting beta2 agonists (LABAs)


Salmeterol, formoterol and indacaterol are inhaled LABAs. Salmeterol and formoterol are licensed for use in both asthma and COPD and are used twice daily. Indacaterol is licensed for COPD only and is used once daily. These inhalers are sometimes referred to as ‘protectors’.





Inhaled corticosteroids (ICS)


The anti-inflammatory actions of steroids are able to control the inflammatory processes in asthma. No steroid inhaler is licensed for use in COPD. Two combination inhalers (LABA+ICS) at specific doses are licensed for COPD.


The inhaled route allows small doses of steroid to be used, minimizing the risk of systemic effects. The ideal inhaled steroid’s properties would include:


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Jun 24, 2016 | Posted by in PHARMACY | Comments Off on Inhaled route

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