What is a Randomized Clinical Trial?

Randomized Clinical Trials – Overview

The Food and Drug Administration (FDA) approves new medications and therapeutic agents for use. FDA approval is based on the results of clinical trials and studies that test the safety profiles and efficacy of the target drug.

One of the most well-founded methods for testing the efficacy of new treatment modalities and options is a randomized clinical trial (RCT).

What is a Randomized Clinical Trial?

An RCT is an interventional study that involves two distinct groups of study participants to test the effectiveness of a specific medical treatment.

This study type was formed in the 1930s by researchers to reduce bias often seen in the past with clinical studies.

In an RCT, participants are divided into two groups: the interventional group and the control group.

As the name describes, the interventional group receives the drug or therapy that is being studied and the control group receives either a placebo drug, fake treatment, or no treatment at all.

The presence of a control group allows researchers to compare the effects of the treatment with no treatment or a placebo, thereby assessing the treatment’s effectiveness rather than its effectiveness in all patients.

If the disease progression or regression in a control group that hasn’t received the treatment is the same as in the interventional group, it suggests that the drug may not be effective, and observed health changes could be due to other factors.

It is important to note that an RCT can have more than one control group and can assess more than one treatment at a time. It can also be performed for different reasons, such as to test the effectiveness, inefficacy, and neutrality of treatment.

How is a Randomized Clinical Trial Performed?

An RCT is the gold standard of all clinical trials and is the preferred method of experimental study by the FDA. For an RCT to be performed, three important factors need to be present:

  • Two groups of study participants need to be selected, both of which must have the same illnesses.
  • Study participants are randomly assigned to either the interventional group, which receives the treatment, or the control group, which does not.
  • Blinding is employed so that neither the participants nor the researchers know who belongs to the control or interventional group to reduce bias. This is to reduce biased results, as doctors or patients may have personal factors resulting in skewing of data. However, RCTs can be unblinded or open in cases where blinding is not possible, for example, if the treatment is a form of physical therapy that requires patients to be aware of their therapy.

The study’s results are statistically analyzed to determine the probability of false positives and false negatives. Then, they are subjected to peer review and eventually review by the journal before they can be published.

Why Randomized?

The main reason behind randomization is to prevent selection bias in the study. Selection bias is grounds for disqualification from the clinical trial and should be avoided at all costs.

If randomization is not performed, there is a possibility that doctors or patients may report biased results.

For example, in a study to determine the inefficacy of a drug, a doctor or researcher may assign a patient with low chances of recovery to the interventional group.

This would prove the study’s hypothesis, but the results would be completely skewed and biased. RCTs are preferred to prevent this.

Advantages of Randomized Clinical Trials

RCTs are the backbone of scientific studies and the main advantage of these, apart from those mentioned above, is that they conduct thorough research and can improve clinical practices.

Many RCTs have scientifically proven and concluded that certain clinical practices were wrong and that changing them would benefit patients.

Disadvantages of Randomized Clinical Trials

RCTs are the gold standard of scientific studies. However, certain disadvantages explain why they are not performed and completed more frequently:

  • RCTs are extremely costly and time-consuming. On average, RCTs can be costly, often requiring millions of dollars and several years to complete, with timeframes and costs varying widely depending on the scope and scale of the study. This means that the financial reimbursement is delayed and finding funding for that long may be difficult.
  • A larger sample size is required. RCTs are performed for long periods and have a high risk of participants either dropping out or losing contact.
  • Possible conflict of interest. Depending on the funding for the study, there has been a significant link between pharmaceutical companies funding an RCT and positive results being reported. This is a conflict of interest, and there are now rules preventing doctors from getting funding from the companies that manufacture the drugs they are studying.


    • Chalmers TC, Smith H Jr, Blackburn B, Silverman B, Schroeder B, Reitman D, Ambroz A (1981). “A method for assessing the quality of a randomized control trial”. Controlled Clinical Trials. 2 (1): 31–49.
    • Bhandari M, Busse JW, Jackowski D, Montori VM, Schünemann H, Sprague S, Mears D, Schemitsch EH, Heels-Ansdell D, Devereaux PJ (2004). “Association between industry funding and statistically significant pro-industry findings in medical and surgical randomized trials”. Can Med Assoc J. 170 (4): 477–80.
  • Johnston SC, Rootenberg JD, Katrak S, Smith WS, Elkins JS (2006). (PDF). Lancet. 367 (9519): 1319–27.

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Current Version
July 11, 2021
Written By
Shubham Grover
April 17, 2024
Updated By
Andleeb Asghar, PharmD

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