The Chemistry of Asthma Inhalers 2016

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If you’re an asthma sufferer, you likely need at least one inhaler to keep your symptoms in check – or maybe even two different types. Commonly, those afflicted with asthma will have both a blue and a brown inhaler. Whilst the colours can vary, the purpose of the chemical compounds contained therein differ dependent on the particular inhaler.

The formulation in inhalers isn’t actually all drug – it will also contain a propellant, as well as small quantities of stabilising compounds. The propellants used were formerly chlorofluorocarbons (CFCs), but due to concerns about their destructive effect on the ozone layer, these started to be replaced with hydrofluoroalkanes (HFAs) in the 1990s (though they were not completely phased out from manufacturing until 2012)*. This replacement had an unexpected beneficial effect, in that, for budesonide, it decreased the size of the liquid particles in the mist produced on spraying the inhaler. This fact alone caused the effectiveness of the drug budesonide to increase by a factor of 2.6.

Broadly speaking, drugs for asthma can be split into two types: relievers, and preventers. The purpose of each is fairly self-explanatory: relievers are used for the relief of asthma symptoms when they become apparent, whilst the preventers are used to help stop these symptoms appearing in the first place. Different chemical compounds are required depending on which of the two results we want to accomplish.

The primary compound used in reliever inhalers, commonly coloured blue, is salbutamol (known as albuterol in the US). This compound is what’s known as a bronchodilator; it, and other similar compounds, work by stimulating receptors in the airway muscles, causing them to relax and widen, and providing relief from asthma symptoms. It’s these inhalers that asthma sufferers turn to in the case of an asthma attack. The inhaler itself ‘nebulises’ the liquid it contains, turning it into a very fine mist that can be inhaled, then act on the muscles in the lungs.

Reliever drugs are by necessity fast-acting, reaching their peak effect between 5-20 minutes after dosing, and lasting for up to two hours. As such, they provide more or less immediate relief from asthma symptoms. However, they don’t act as preventers for future asthma symptoms; for that, different compounds are needed.

The preventers are usually steroids, and are often taken nebulised in a similar manner to the relievers. One of the most common is budesonide, often sold under the trade name ‘Pulmicort’; another that is commonly used is beclamethasone dipropionate. These steroid medications work by reducing inflammation in the lungs, and helping to keep the airways open, and reducing the sensitivity of the lung tissue to triggers. Unlike the relievers, preventers are no use for relief from asthma attacks; instead, regular dosing is required for their effects to be apparent.

Usually, preventers will be taken daily, and it can take up to 8 days for any beneficial effects to kick in. Further to that, it may take up to 6 weeks for the medication to reach its peak effect. Even once the preventative effect is noticeable, this can quickly fade if regular dosing is not maintained. For some patients, combination inhalers are offered, which perform the function of both reliever and preventer.

Both salbutamol and budesonide are on the World Health Organisation’s list of essential medicines, which it defines as the most important medications required for a basic health system. Budesonide actually also has another use in the treatment of Crohn’s disease. Without either of these compounds, life for asthma sufferers would be a lot more difficult – and potentially shorter!

*An earlier version of this article failed to clarify that though replacement of CFCs commenced in the 1990s, they were not completely phased out from manufacturing until much later (in 2012). 



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