Adrenal Suppression and Systemic Bioavailability Across Inhaled Corticosteroid Delivery Technologies in Children With Asthma: A Systematic Review
This systematic review of five pediatric studies concludes that current evidence is insufficient to assert that any specific inhaled corticosteroid delivery technology is consistently safer regarding adrenal suppression, highlighting the need to evaluate safety based on specific drug, dose, formulation, and device combinations rather than broad device class assumptions.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every child with persistent asthma carries a small canister or inhaler that delivers a powerful medicine directly into their lungs. These medicines, known as inhaled corticosteroids, are the cornerstone of treatment, working quietly to calm the swelling and irritation that make breathing difficult. They are designed to stay in the airways, but the human body is a connected system, and a tiny amount of this medicine can sometimes slip past the lungs and enter the bloodstream. Once in the blood, this medicine can reach the adrenal glands, two small organs sitting atop the kidneys that act as the body's natural stress-response factory. When these glands are exposed to too much outside medicine, they can slow down their own production of natural hormones, a condition called adrenal suppression. This can be dangerous if a child faces a serious illness or injury, as their body might not be able to summon the extra energy it needs to cope.
For years, doctors and parents have wondered if the type of device used to deliver the medicine changes this risk. Some children use pressurized canisters that release a fine mist, others use dry powder inhalers that require a quick, deep breath, and some use nebulizers that turn liquid medicine into a mist over several minutes. There is also the question of whether the propellant inside the canister matters, as older versions used chemicals that damaged the ozone layer, while newer ones use different gases. The central question for researchers was whether one of these delivery methods is inherently safer than the others, or if the risk of affecting the adrenal glands depends more on the specific drug, the dose, and how well the child uses the device.
A team of researchers set out to answer this by gathering every available study that looked at children with asthma and measured how their bodies reacted to these different delivery systems. They did not just look at whether the asthma got better; they focused specifically on the body's internal chemistry, searching for signs that the adrenal glands were being suppressed. They examined studies that measured levels of cortisol, the primary hormone produced by the adrenal glands, in the urine or blood of children using various inhalers. The goal was to see if switching from one type of device to another, while keeping the medicine the same, would result in a measurable difference in how much of the drug the body absorbed or how much the adrenal glands slowed down.
The researchers sifted through hundreds of records, eventually narrowing their focus to five high-quality studies that directly compared different devices in children. These studies involved a total of 751 participants, ranging in age from toddlers to teenagers. The team looked at comparisons between older and newer types of pressurized canisters, between dry powder inhalers and mist inhalers used with a spacer, and between different nebulizer systems. They were careful to separate studies that compared the exact same drug and dose delivered by different machines from those that changed the drug or the dose at the same time, as the latter would make it impossible to tell if the device or the medicine was the cause of any changes.
The results of this careful review suggest that there is no single type of device that is consistently safer for the adrenal glands. When the researchers looked at children using the same dose of beclomethasone, a common asthma medicine, delivered by either the older or the newer type of canister, they found no significant difference in the levels of cortisol in the children's urine. The body's response was essentially the same regardless of the propellant used. In another comparison involving fluticasone, the newer canister did show lower levels of the drug circulating in the blood, but the study did not provide clear data on whether this translated to a safer outcome for the adrenal glands.
The most distinct finding came from a small study comparing a dry powder inhaler to a mist inhaler used with a spacer device. In this specific case, the children using the dry powder inhaler showed a greater drop in their urinary cortisol levels compared to those using the mist inhaler with the spacer. However, this was a small study with only fifteen children, and the researchers caution that this single result cannot be taken as a broad rule for all children or all medicines. When the team looked at studies that mixed different drugs or doses, the results were too varied to draw a clear line between the device and the risk.
Ultimately, the evidence gathered in this review does not support the idea that one broad category of inhaler is universally safer than another. Instead, the risk of adrenal suppression appears to depend on a complex mix of factors: the specific type of steroid molecule, the exact dose given, the formulation of the medicine, and how much of it actually reaches the lungs versus how much is swallowed. The study highlights that the way a child uses the device—whether they coordinate their breath correctly, how well they fit a mask, or how clean the spacer is—can change the amount of medicine delivered just as much as the device itself.
The authors conclude that doctors and parents should not assume that switching to a newer or different type of inhaler will automatically reduce the risk of adrenal problems. The safety of the treatment depends more on the details of the prescription and the technique of the user than on the label of the device. While the review found no broad pattern of one device being consistently superior, it also noted that the available data is limited and often comes from small groups of children. Future research will need to compare devices more carefully, keeping the drug and dose exactly the same, to provide clearer answers. For now, the best approach remains ensuring that every child uses their specific inhaler correctly and is monitored for any signs of systemic effects, rather than relying on the type of device alone to guarantee safety.
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