ABC of asthma; Methods of delivering drugs
BMJ 2005; 331 doi: https://doi.org/10.1136/sbmj.0511406 (Published 01 November 2005) Cite this as: BMJ 2005;331:0511406
- John Rees, consultant physician1
- 1Guy's, King's and St Thomas's School of Medicine, London SE1 9RT
This article is adapted from the 5th edition of the ABC of Asthma in Adults, which will be published at the end of the year and will be available from www.hammicksbma.com
Various inhaler devices and formulations have been developed to deliver drugs efficiently, minimise side effects, and simplify use. With the range of devices available nearly all patients can take drugs by inhalation. All the available devices used appropriately can provide adequate drug to the airways. Inhalers should not be prescribed without checking that the patient can use the device satisfac torily. This should be rechecked on subsequent visits as errors can develop and interfere with treatment. Some drugs, such as leukotriene receptor antagonists and theophylline, cannot be given by inhalation.
Metered dose inhalers
Inhalers deliver the drug directly to the airways. Even when a metered dose inhaler is used properly, however, only about 10% of the drug reaches the airways below the larynx. Nearly all the rest of the drug gets no further than the oropharynx and is swallowed. This swallowed portion may be absorbed from the gastrointestinal tract, but drugs such as inhaled corticosteroids are largely removed by first pass metabolism in the liver. Absorption directly from the lung bypasses liver metabolism.
Use of spacer devices
Match the inhaler and spacer
Inhale as soon as possible after each single actuation
Empty the chamber by single large breaths or tidal breathing
Clean chamber monthly
Wash chamber in detergent and water and leave to dry
Wipe any detergent from mouthpiece
Replace spacer every 6-12 months
The inhaler should be shaken and then fired into the mouth shortly after the start of a slow full inspiration. At full inflation the breath should be held for 10 seconds. The technique should be checked periodically. About a quarter of patients have difficulty using a …
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