Why Inhaler Corticosteroid Side-Effects are Negligible
Inhaled corticosteroids (ICS) are considered a top-line treatment of asthma. One of the main reasons is because they are proven both effective and safe for controlling asthma. Safe essentially means side effects are considered negligible, especially when compared with systemic corticosteroids. The question of the day is: how is it that side effects of ICS are negligible. Let's investigate.
They offer a low dose of ICS
It was realized during the 1950s that systemic corticosteroids taken by mouth or injected into a muscle greatly improved asthma control. However, by the 1960s it was learned that systemic corticosteroids come with many unwanted side effects. By the 1980s, it was determined that applying low doses of ICS directly to airways by inhaling the medicine also resulted in improved asthma control, although with a significant reduction in the risk for side effects.
How low is low dose?
One study published in 1975 showed that 400 mcg of beclomethasone was equivalent to 5-7mg of prednisone. 1 You have to keep in mind that this was when chlorofluorocarbon (CFC) was used as the propellant. Today, hydrofluoroalkane (HFA) is used as the propellant for beclomethasone. Studies show that HFA beclomethasone is better distributed throughout the airways compared with CFC beclomethasone. This means that a lower dose is needed to obtain the same results. And, the benefit of this lower dose is an even lower risk for side effects. The modern version of beclomethasone is QVAR, and we can probably assume the dose is lower than 5mg prednisone. Dry Powder Inhaler (DPI) ICS are also better distributed to airways than the old CFC inhalers, so this also allows for lower dosing and a lower risk for side effects.
Most of the medicine is wasted
Let's assume your dose of ICS is equivalent to 5mg prednisone. It's not, it's probably less than that, but let's assume it is. Of that 5m, nearly 90% of that medicine is wasted. Studies show that 15% of medicine inhaled by an HFA inhaler plus an inhaler (assuming good technique) makes it to your airways where it's needed, and only 13% of medicine inhaled by a DPI makes it to your airways. 2 So, the fact that most of the medicine is wasted also results in a reduction of side effects. Note: Scientists are aware of this fact, and this is why the dose is set where it is, as opposed to having you inhale a lower dose of medicine (say, 2mg of prednisone as opposed to 5mg).
The medicine is applied directly to the airway
When you take systemic corticosteroids, the medicine makes it to your intestinal tract, where it is broken down by your liver. Much of the medicine is excreted in urine. However, enough enters your circulatory system to reduce inflammation (in your lungs and other places) and cause systemic side effects. When you inhale a low dose of the medicine, it is directly applied to your airways (similar to when you apply lotion directly to your skin), obtaining the same reduction in airway inflammation. Only a scanty amount of the medicine that impacts in your upper airway is swallowed and enters your system. Only a scanty amount of medicine comes into contact with blood vessels in your lungs, where it enters your system. This is one of the main reasons for negligible side effects. 3-5
Proper technique reduces side effects even more
Studies have confirmed if you use proper inhaler technique, and if you use a spacer with your HFA inhaler, that this greatly reduces side effects even more. Large particles of the inhaled medicine impact in the spacer, rather than your upper airway. Likewise, if you rinse your mouth out with water, gargle and spit, this removes much of the medicine particles that impacted in your upper airway, preventing these particles from being swallowed and entering your system.
So, you can now see why side effects of systemic steroids are generally considered negligible. Still, there is a likelihood that side effects can still occur. When you observe side effects and you think the inhaler is the cause, talk to your doctor. Chances are there is a simple change you can make to remedy the situation, such as making sure you are using the device correctly. Sometimes the remedy is a simple reminder to rinse or spit after using the product. Sometimes, and this usually occurs when you are new to a product, side effects may be intolerable. Since side effects vary from one device to another, and one ICS product to another, the remedy here might be a simple change to a new device or a new ICS product. So, in the rare chance you experience side effects to ICS, do not give up. Talk to your doctor, as the solution may be a subtle change.
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