Inhalers: Medications, Indications and Devices

Introduction

Inhalation therapy has long been practiced in many parts of the world. In China there are records of inhalation treatment of asthma going back to 2600 BC. It was recorded on an ancient Egyptian papyrus in 1554 BC, and in South and Central America tobacco was being used therapeutically and recreationally 2000 years ago. Some methods of inhalation were as simple as throwing herbs onto hot bricks which caused vapourisation of the active ingredient so that it could be inhaled, to the use of pipes for tobacco, and incense burners.

The benefit of delivering medication directly to the lungs has been understood for more than two hundred years. The word ‘inhaler’ was first used by the English physician John Mudge in 1778 to describe his adaptation of a pewter tankard used for inhaling opium vapour to treat cough. The devices have changed, but the principles that were developed are still in use.

The first modern inhalers were developed in 1955 and were pressurised metered dose inhalers (pMDI) which contained isoprenaline and adrenaline. The pMDI produced an atomised spray and allowed for more accurate dosing than previous devices. Over the years these have been further developed with different medications, in 1969 salbutamol and in 1972 beclomethasone, as well as improvements in propellants. Chlorofluorocarbons (CFC) were first used, but they have been phased out due to their destructive effects on the ozone layer and have been replaced with hydrofluorocarbons (HFA), which are less damaging; pMDIs are still the mainstay of treatment for both asthma and Chronic Obstructive Pulmonary Disease (COPD).

Dry powder inhalers, which often offer greater convenience to patients and are easier to use, have been developed alongside the pMDI and these have been progressively refined, hence the current plethora of different devices.

Administering medications via inhalation is an ideal way to deliver the active ingredient directly to the area of the lungs where it will work. This manner of topical application often acts more quickly than oral dosing; it allows for smaller doses and significantly reduces side effects as very little of the medication is absorbed systemically. Medications are given by inhaled therapy for several conditions and reasons, including antibiotics for chest infections in cystic fibrosis, iloprost for pulmonary arterial hypertension (not available in Australia), analgesics and anaesthetics. This lecture describes the medications used in inhaled devices for the treatment of asthma and COPD, also known as chronic obstructive airways disease (COAD).

While there are oral treatments for these conditions, and some of the medications used in inhalers are also used in nebulisers, we focus on inhalers.

There is some crossover between asthma and COPD, but they are essentially long term conditions involving episodes of shortness of breath (SOB), wheezing, inflammation and infections. Asthma often has an allergic component and may be controlled by identifying trigger factors and avoidance of these factors; and the SOB and wheezing is commonly reversible. COPD is a chronic condition often developed in smokers, poorly controlled asthmatics, and in people who have worked for extended periods in a dusty atmosphere.

In this case the condition is not fully reversible and treatment consists of reducing further damage by stopping smoking, improving airway access, and reducing infection and other exacerbations.

Medications

Do you know what medications are used in inhalation therapy and why some combinations are used? What are preventers and relievers? What is their place in the treatment of both asthma and COPD? What are potential side effects? What is the rationale behind combination therapy? This lecture answers these questions and discusses the following medications:

Bronchodilators

• short acting beta agonists

– salbutamol
– terbutaline

• long acting beta agonists

– eformoterol
– indacaterol
– salmeterol

• the anticholinergics

– short acting ipratropium
– long acting tiotropium

Corticosteroids

• beclomethasone
• budesonide
• ciclesonide
• fluticasone

Cromones

• cromoglycate
• nedocromil

Devices

Do you know how to use the different devices, why some may be more effective than others in particular situations? And there are many, as seen in Table 1.

Table 1. Asthma and COPD Medications.

The pMDI, with or without a spacer is the only device, other than a nebuliser which does not rely on inspiratory flow rate, all the others need varying rates of inspiratory flow for effective deposition of medication. The Turbohaler^® devices require the greatest flow rate and this can become a problem during exacerbations when lung function deteriorates. If this potential problem is recognised as part of the management plan and an alternative device, e.g. pMDI and spacer is available, the exacerbations may be better controlled and hospital stays avoided, but the important thing to remember is that the most effective device is the one that the patient will use and can use.

The lecture answers some of the above questions, explains the different devices, and provides direction to useful resources and websites which show the available devices and provide instructional videos on how they are used.