If you use an inhaler every day to manage your asthma, you might assume that your medication automatically rules you out of a clinical trial. This is one of the most common concerns we hear from people who are curious about taking part in asthma research. The good news is that in most cases, it does not.
This article explains how asthma medication affects your eligibility, what researchers are actually looking for, and what the process looks like if you decide to find out more.
Why Do People Think Medication Rules Them Out?
It is a natural assumption. Clinical trials test new treatments, so it might seem logical that researchers would only want participants who are not already taking anything. In reality, the opposite is often true.
Most asthma clinical trials are specifically looking for people who are already on medication. Researchers want to understand how a new treatment performs in the kind of real-world situation that most people with asthma actually live in. If you are using a preventer inhaler daily, or a reliever inhaler when symptoms flare, that is completely normal and expected.
What Kinds of Asthma Medication Do Most People Take?
To understand how medication fits into trial eligibility, it helps to know the main types of asthma treatment. According to the NHS, inhalers are the main form of asthma treatment in the UK. There are two broad categories:
- Reliever inhalers (usually blue) are used when symptoms occur. They work quickly to open up the airways.
- Preventer inhalers contain a steroid medicine and are taken every day to reduce inflammation in the airways, even when you feel well.
Some people also use combination inhalers that do both jobs, or take tablets such as leukotriene receptor antagonists (LTRAs) alongside their inhaler. You can read more about the full range of asthma treatments on the NHS asthma treatment page.
The fact that you are on any of these treatments does not automatically exclude you from a clinical trial.
What Do Asthma Trials Actually Look For?
Each trial has its own set of inclusion and exclusion criteria. These are the rules that determine who can and cannot take part. They exist to keep participants safe and to make sure the research produces useful results.
For asthma trials, the criteria often centre on whether your asthma is stable and controlled. This means:
- Your symptoms are being managed with your current medication
- You have had a confirmed asthma diagnosis for a certain period, often at least 12 months
- Your lung function results (measured in a breathing test called spirometry) fall within a particular range
- You have not had a severe asthma attack requiring hospital admission very recently
Being on a preventer inhaler, for instance, is often a sign that your asthma is being actively managed rather than left untreated. This can actually work in your favour when it comes to eligibility.
When Might Medication Affect Your Eligibility?
There are some situations where your current medication could affect whether you can take part in a specific trial. This is not about penalising you for being treated; it is about making sure the research is safe and meaningful.
Does “Controlled Asthma” Mean My Symptoms Have to Be Perfect?
Not necessarily. The phrase “controlled asthma” in a clinical trial context does not always mean your asthma is perfectly managed with no symptoms whatsoever. It usually means your condition is stable enough that it has been consistently managed with your current treatment over a period of time.
In fact, many trials are specifically looking for people whose asthma is not fully controlled despite being on standard medication. This is because researchers want to test whether a new treatment can do a better job. If you still experience symptoms even though you are using your inhaler regularly, that might make you a good candidate rather than a poor one.
What Happens at the Screening Stage?
Before you join any trial, you go through a screening process. This is where the research team checks whether you meet the eligibility criteria. It typically involves:
- A review of your medical history and current medications
- A breathing test (spirometry) to measure your lung function
- Blood tests and a general health check
- Questions about your asthma symptoms and how often you use your inhaler
You do not need to stop taking your medication before a screening appointment. The team will review everything you are currently taking and explain clearly whether it affects your suitability for that specific study.
If you do not qualify for one trial, you may still be a good fit for another. New studies open regularly, and the research team can keep your details on file.
Can I Keep Taking My Medication During a Trial?
In many cases, yes. Whether you can continue your usual medication during a trial depends on the study design. The research team will explain this clearly before you agree to take part.
Some trials allow participants to carry on with their existing asthma treatment alongside the new study treatment. Others may ask you to change or pause certain medications under close medical supervision, and only if it is safe to do so.
You will never be asked to stop your medication without a full explanation and without the appropriate safety monitoring in place. Your wellbeing is the priority throughout. For more on what to know before you take part in a trial, including your rights and what the informed consent process involves, our information hub has a dedicated guide.
Frequently Asked Questions
I only use a blue reliever inhaler. Can I still take part? Yes, in many cases. Using a reliever inhaler as needed is very common among people with mild to moderate asthma. Whether this affects your eligibility will depend on how often you use it and the specific requirements of the trial you are interested in.
I recently had my medication changed by my GP. Does this affect things? Possibly. Some trials require your medication to have been stable for a set period, often three to six months, before you can enrol. This is to make sure the research results are not affected by a recent change. If your dose was adjusted recently, it is still worth enquiring as the timing may work out.
I take tablets for asthma as well as inhalers. Is that a problem? Not automatically. Many people take LTRAs or other oral medication alongside inhalers. The research team will review all your medications as part of screening and advise you accordingly.
What if I have other health conditions as well? Having other health conditions does not rule you out. Researchers will consider your overall health as part of the screening process. Some conditions or medications may affect eligibility for specific trials, but this is always assessed individually.
How to Find Out If You Qualify
The only way to know for certain whether your current medication affects your eligibility is to get in touch with a research team. The screening process is free, there is no obligation to continue if you change your mind, and you can withdraw at any point without it affecting your normal medical care.
At Clinical Trials UK, our team is happy to answer your questions before you commit to anything. You can view our current asthma clinical trial to find out more about the study we are running, including an overview of what participation involves.
If you want a more detailed breakdown of the types of criteria typically used, take a look at our full eligibility guide for our asthma trial, which covers everything from breathing test requirements to lifestyle factors.
You can also browse our frequently asked questions for general information about taking part in clinical research.
Taking asthma medication is not a barrier. For most people, it is simply part of living with a long-term condition. The research community understands this, and trial eligibility criteria are designed with that in mind. If you have been putting off enquiring because you assumed your inhaler would rule you out, it is well worth finding out the facts.
