What Is An Open Label Clinical Trial?

Discover what is an open label study, what makes it different from other clinical trials, and why open label clinical trials are so important.

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Reviewed by Nam Tram, PharmD

Published 20 December 2023

When it comes to identifying new and effective medical treatments, clinical trials are essential to determine the safety and viability of new drugs and interventions. Clinical trials can vary in duration and the number of participants, but most follow a similar format to conduct a thorough and worthwhile study.

An open-label clinical trial is a type of study that offers maximum transparency, with both participants and researchers informed about which treatment is being administered. In this article, we will provide an overview of what an open-label clinical trial is, including its advantages and limitations.

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Understanding Open-Label Clinical Trials

Many clinical trials are based on a ‘double-blind’ approach, with both researchers and participants in the dark about which treatment will be administered. This is to avoid any bias towards certain drugs or treatments, resulting in a fairer study.

Open-label clinical trials, however, let both researchers and participants know which medical intervention is being given, with no important details withheld. This helps researchers make an informed comparison between two or more interventions and their long-term effects.

How do Open-Label Studies Compare to Other Clinical Trials?

Open-label clinical trials are specifically treatment trials and not observational studies. Although there are many different types of clinical trials, the most direct comparison is with blinded clinical trials.

Open-label clinical trials vs blinded clinical trials

There are many key differences between an open-label trial and a blinded clinical trial, which are often considered opposites, the following are the most common differences:

  • Participants typically prefer open-label trials as they are more transparent and they are fully informed about the medical intervention they will receive.
  • In a blinded trial, patients are not told which drug or treatment they are given, removing an element of bias in terms of participants knowing whether they are taking a placebo or not. If participants are aware that they are being given a placebo, then they may question how they are benefitting from the trial.
  • Although open-label trials can be randomized, participants are usually hand selected based on their characteristics.
  • Open-label trials sometimes do not have a placebo group, classifying them as uncontrolled. This means all participants will receive the same treatment.
  • Blinded clinical trials can be separated into two categories: single-blind studies and double-blind trials:
    • In a single-blind study, researchers know which treatment has been administered but the participant does not.
    • In a double-blinded trial, neither the researchers nor the participants know what treatment has been given, whether it is the new drug or a placebo.
  • The possibility of bias and a lack of control means open-label clinical trials are usually considered less valuable than a blinded trial.

What are the Advantages of Open-Label Clinical Trials?

Many participants who have completed a clinical trial may then be eligible to continue their treatment in an open-label clinical trial for an extended period. This additional course of treatment is one of the main benefits for patients.

As participants have assurances about the type of treatment they will receive, the trial will resemble normal medical treatment, taking into consideration their best interests, making individuals often much more willing to participate in an open-label trial than a blind one.

From both the participants and researchers perspective, there are several benefits to open-label clinical trials which are outlined below.

They help understand safety

When compared to ‘double-blind’ trials, open-label trials enable an extended follow-up period as participants can continue with the treatment under study for a longer period of time. This gives researchers more opportunity to study the long-term effects of the medical intervention, which usually would not be possible in blinded trials that have shorter timeframes.

As a result, open-label trials may better reflect real-world scenarios in terms of how long a participant would use a drug or treatment. As these trials are usually non-randomized clinical trials, researchers can select a more diverse group of participants to include a range of demographics. This can include people of different ages, genders, ethnicities, and medical conditions.

This diversity allows researchers to better understand the levels of safety for a wider section of the population, helping to identify side effects that may only affect a certain type of person.

They provide better interaction between investigators and participants

As researchers are aware of what drug or treatment is being administered to a participant, they can make better decisions based on the participant’s feedback. This allows decisions to be made to provide better outcomes but it could also result in some bias, impacting the overall success of the trial.

One possible instance of bias could be an eagerness to collect positive data because a researcher has a strong belief in a drug. This could result in outcomes being skewed and findings being misreported.

What are the Limitations of Open-Label Trials?

Like any study, an open-label clinical trial does have certain limitations that may make them less suitable for specific types of research and desired outcomes. These limitations can result in disadvantages such as a higher rate of participant dropouts, participants experiencing placebo effects, but also validity concerns caused by participants not disclosing the full extent of any side effects.

Bias can also be common in open-label clinical trials, with researchers sometimes selecting participants based on the specific characteristics needed for the trial, rather than selecting from a broader spectrum of people.

Open-label trials and the placebo effect

When a participant knows they are receiving an active treatment or a placebo, they may question the level of benefit they are receiving. Patients who are receiving a placebo may feel aggrieved that they are not being given the best available treatment, if the alternative drug is still in its experimental stage.

Unfortunately, this can increase the dropout rate of open-label clinical trials and also make participants less willing to report important information to researchers.

Open-label trials bias concerns

As researchers are aware of the treatments involved in the trial, they may apply some bias when analyzing the results, potentially favoring the new treatment and impacting the validity of the outcome.

Patients can also skew outcomes by underreporting the side effects of the new treatment or making claims that it is more effective than it actually is. This is usually a psychological factor, as patients are reluctant to disclose negative feedback as they do not want to disappoint researchers. Unfortunately, this is a frequent occurrence in open-label trials.

Open-Label Trials and Ethical Concerns

Open-label trials present a few ethical concerns that participants should be aware of. One such concern is the inclusion of participants that may have had a reaction to previous treatments. If they have previously taken part in a clinical trial, then the outcome data may not have been released by the time an open-label trial begins, potentially putting the participant at risk of serious side effects.

Effectively, a participant may have given ‘informed consent’ without knowing if the treatment could have an adverse effect on them.

In all clinical trials, the privacy and confidentiality of participants should be maintained at all times. The need for privacy may also be increased if the treatment and condition/disease have a stigma attached to it which could lead to discrimination. Patient confidentiality remains one of the key challenges for clinical trial teams, with many people preferring to keep their participation private.

Conflicts of interest

A somewhat common conflict of interest is if a researcher has financial links to the company that is sponsoring the trial or study, potentially resulting in financial gain if the outcomes are positive and the treatment is approved.

This could cause extreme bias, impacting the researcher's conduct and perhaps even the overall design of the trial. Ultimately, this could also lead them to heavily favor an experimental treatment, regardless of patient outcomes and supporting data.

In such cases, manipulating the results is also made easier because the biased researcher knows who is, and who isn’t receiving treatment. This means that they could be more selective about the relevance of data, disregarding insights that reflect negatively on the experimental drug.

There are also non-financial conflicts of interest, such as a keenness to report positive results to help advance their career or a general interest or belief in a certain drug that makes them hopeful that it is effective.

The Importance of Open-Label Clinical Trials

Safe drugs, new treatments and effective medical interventions cannot be developed and brought to market without clinical trials and extensive studies. Open-label clinical trials are important for providing researchers with more usable data regarding an experimental drug or treatment, such as its side effects and efficacy.

Below are some of the key reasons why open-label trials are important for medical advancements.

  • Open-label trials provide more data for researchers to help them assess the potential benefits and drawbacks of a new drug or treatment. This allows them to make an informed decision on where treatments can be effective and where they cannot.
  • They can help to improve the design and development of new medical interventions. Without a practical design, new treatments can suffer delays in terms of being introduced to the market.
  • This type of trial provides real-world evidence in terms of the overall safety and efficacy of a drug or treatment. This can be vital in the study of rare or chronic diseases.
  • Added flexibility also makes it possible to include a diverse range of patient populations and alternative treatments. Again, this is extremely beneficial when it comes to investigating diseases and conditions that are little understood, or cause a wide variety of symptoms.

The Future of Open-Label Clinical Trials

Like any area of medical research and science, the future of open-label clinical trials will likely be shaped by advancements in technology, changing regulations, active engagement, and ethics. New technology and adaptive trial designs will likely play the biggest role in terms of the future of open-label clinical trials.

The role of technology

Technology plays a significant role in the medical sector, especially when it comes to gathering insights and valuable data. Technology such as wearable monitoring devices, electronic databases, advanced analytics, and telemedicine have all changed the medical landscape in recent years and will continue to make a big difference. This is especially the case for open-label trials.

Wearable devices, for example, allow real-world and real-time data to be collected to better monitor patient outcomes and the effects of ongoing treatment. This, combined with advanced analytics allow researchers to work with more accurate data that can be combined with patient feedback.

Adaptive trial designs

Adaptive trial designs allow researchers to make certain changes during an open-label clinical trial to improve patient outcomes. This is based on up-to-date data that can be used to determine the best course of action for individual participants. By adapting trials, researchers can provide the best-estimated treatment, which in turn, provides more valuable outcomes.


Open-label clinical trials are clinical studies in which both the researchers and the participants are aware of the treatment being administered, whether that is an experimental drug or a placebo, making them the opposite of blinded trials. This can result in a higher rate of participation compared to other trials.

In addition, these trials help research teams gather more valuable data which can improve the chances of new drugs reaching the market.

The downside to open-label trials is that an element of bias can be present with the researchers as they know what treatment is being administered or have financial ties to the trial itself. Furthermore, patient dropouts can also be higher among people who feel the trial is not benefiting them.

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