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Analysis: Do inhalers ‘damage lungs’?

Winter presents unique hazards to people with lung disease. Air quality decreases due to pollution trapping, fuels like wood, coal and paraffin are burnt for warmth and influenza (flu)  infection rates surge.

Many people will consult doctors for relief from their tight chests and shortness of breath.

Enter inhalers: the solution to the problem of how to administer medication directly to the lungs. They have become important in managing “obstructive” lung diseases, like asthma and chronic obstructive pulmonary disease (COPD).

Because so many people need inhalers we should all be worried by news reports published by the Star newspaper in South Africa claiming that studies have shown that “inhalers can damage lungs”.
 

Original source unclear


Despite the alarming headline, the short article aims to raise awareness of COPD, and how it is frequently misdiagnosed. It is a republished version of an original story that was published in the UK’s Mail Online.

The connection between lung damage and inhaler use is never clearly explained in the Star’s version of the report. Instead it refers to the effect of inhaled corticosteroids (a class of medication used to suppress inflammation and the immune system) on the lungs, and concern that these drugs leave users more susceptible to infections.

We contacted the Star and the original Mail Online journalist to ask which study they were reporting on. We did not get a reply to our emails.

Without these answers, we are left with two important questions. Are inhalers themselves causing lung damage? Do inhaled corticosteroids cause lung damage?
 

Inhalers have been tested for safety


Inhalers are a drug delivery mechanism and are used to administer a variety of medications. A blanket statement like “inhalers can damage lungs” is like saying “eye drops can damage eyes” or “creams can damage skin”.

Inhalers come in two variants: metered-dose inhalers and dry-powder inhalers.

Metered dose inhalers consist of a metal canister, which contains both the drug and the substance that carries the drug — the propellant. The standard propellant used in modern inhalers has been shown to be so safe that dosages 200 times and upwards of the expected human exposure have been found to be non-toxic. This is in part because most of the inhaled propellant is exhaled again almost immediately.

Dry powder inhalers, on the other hand, are typically made from plastics. They contain a mixture of the active medication (in powder form) and a stabilising agent (typically lactose). The stabilising agent must be both safe to inhale and prevent clumping of the medication, so that the medication is delivered evenly to the lungs. This substance must also be non-irritating and be able to be broken down by the body or swept up and out by the cells lining the airways.

How do we know lactose is safe? As with the propellant in metered dose inhalers, lactose was first tested. One of the earliest reviews was an extensive series of animal studies on rats, dogs, monkeys and macaques. Researchers found no evidence that lactose had side effects on the lungs.

Other studies have investigated if dry powder inhalers are more dangerous than metered dose inhalers. A Brazilian study showed that there was no difference in side effects or efficacy of drug delivery. A Swedish study found that lactose had no negative effect on the airways.
 

Are steroids harmful to the lungs?


If research shows that inhalers are safe, that leaves one final avenue of investigation.

Corticosteroids — a type of steroid — are part of the typical treatment in the management of asthma. They have been demonstrated to improve quality of life, reduce risk of death from asthma and decrease hospitalisation rates. This is largely thanks to their ability to control inflammation.

“There may be some side effects to inhaled steroids, but significantly less so than taking these drugs orally,” Professor Richard van Zyl-Smit, head of the University of Cape Town’s Lung Institute, told Africa Check.

Taking a prolonged course of oral corticosteroids is associated with a host of side-effects such as osteoporosis, hypertension, weight gain, mood changes and cataracts.

Unlike in asthma, the narrowing of the airways in chronic obstructive pulmonary disease (COPD) is typically thought to be permanent, which means steroids have a less clear role to play in treatment. But what does the data suggest?

In 2012, the Cochrane group published a meta-review analysis of 55 studies. They found that using inhaled corticosteroids for more than six months did not significantly stall the slow but steady decline of lung function in COPD. Despite not changing the long-term outcomes of the disease, there was a minor decrease in symptoms and a small associated improvement in quality of life. On the other hand, the same review identified another more worrying trend: higher doses of inhaled corticosteroid were associated with a modest increase in hospitalisations for pneumonia.

This is the finding that brings us closest to “lung damage”. It’s important to distinguish that it’s not that the drug itself that damages the lung. It’s likely that the drug’s ability to suppress inflammation and hinder the disease-fighting function of the immune-cells may increase the risk of lung infections.

In 2014 the Cochrane society published another review, this time specifically analysing the connection between inhaled corticosteroids in COPD and pneumonia. Depending on the type of inhaled steroid used, pneumonia admissions to hospital were increased by 8 to 12 additional admissions per 1,000 people treated per year, but the difference in deaths between study groups was not significant.

Could the same be true for asthma? A group of researchers from the UK reported a two-fold increase in the risk of pneumonia or lower respiratory tract infection with the highest dose of inhaled corticosteroids.
 

The benefits outweigh any harm


In both asthma and chronic obstructive pulmonary disease, high-dose inhaled corticosteroids have been shown to slightly increase the incidence of hospitalisations for infections of the lung, which makes sense because of the immune-impairing effect of corticosteroids. But these increases are small in absolute terms.

In asthma the balance of positive effects on quality of life and general outcomes greatly favours the use of corticosteroids. In the case of chronic obstructive pulmonary disease its best to determine their use on a case-by-case basis with the aid of a doctor.

Despite this side effect, to claim that all inhalers — or specifically corticosteroids — can damage lungs is not only unsubstantiated but harmful.

“There isn’t really an argument over whether they harm the lung,” said Prof van Zyl-Smit. “Rather they save lives from asthma and there are many articles showing the benefits of inhalers”.

Petrie Jansen van Vuuren is a medical doctor based in Gauteng, with a postgraduate background in human physiology research at the University of Pretoria.

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