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Clinical Trial | Phases Of A Clinical Trial Explained

A clinical trial is a medical research carried out on people, who voluntarily participate in these studies. And who help to discover better ways to treat, prevent, diagnose and understand diseases that affect humans.

Clinical trials can be to test the effectiveness of new drugs or to compare existing treatments, and determine which is more or less beneficial. Before conducting human trials, other safety and efficacy studies are conducted in the laboratory. And if appropriate therapy is considered, research continues and human clinical trials proceed.


What are the phases of a clinical trial?

A clinical trial is a research study conducted involuntarily participating humans that help to test whether a new therapy, drug, or procedure is safe and effective.

They can be of various types and are carried out in different phases. To proceed to the next phase of a clinical trial, the new treatment must have achieved satisfactory results in the previous phase.


Depending on the objectives they pursue, and the different types of clinical trials.

Preventive tests: They test new methods to lower the risk of developing a disease. This implies that healthy people participate in them who may or may not be at risk of developing the disease.

This is the case of clinical trials for the prevention of Alzheimer’s disease in which the research centre of the Pasqual Maragall Foundation, the Barcelona Beta Brain Research Center, participates.

Diagnostic tests: They focus on identifying new tests or procedures for diagnosing a disease.

Detection tests: They test methods of early diagnosis of a disease.

Treatment trials: They investigate new therapies, whether they be drugs, procedures or surgical techniques, to treat a disease.

Quality of life test: The study treatments or procedures to improve the quality of life of people with chronic diseases.

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Clinical trials classified results obtained

Clinical trials can also be classified according to the possibility of being modified according to the results that are obtained. Thus, there are clinical trials with a fixed design or protocol, in which the design is defined before the start of the trial.

And adaptive clinical trials, in which the possibility, of making changes in one or more is defined before the start of the study. More aspects of its design based on the data that is obtained during its realization.

The changes may include modifications in the dose of the drug tested. The number of participants included in the study and even the drugs tested, depending on the results that are obtained.

In the case of Alzheimer’s, for example, the Barcelona Beta Brain Research Center. The research centre of the Pasqual Maragall Foundation, participates in the European EPAD project.

Which will carry out an adaptive clinical trial, for the prevention of the disease to test at the same time. Different branches of treatment and to be able to quickly withdraw drugs that do not show positive results, as well as introduce new ones.

Before deciding to take part in a clinical trial, you need to think about it and listen to your doctor’s opinion. It is advisable to have all the information and resolve any doubts that may arise before making the decision.


Phases of a clinical trial

Before starting a clinical trial with humans, it is necessary to carry out first biological and toxicity tests through in vitro studies (carried out in the laboratory) and in vivo studies (with animals). This phase of preliminary experimentation is called the preclinical phase.

In turn, clinical trials with humans are classified into four phases and, in each of them. The trial must answer different questions about its safety and efficacy.

These are whether the treatment works, whether it has side effects, whether its benefits outweigh its risks. And which participants are most likely to benefit. If the results of the trial in one phase are satisfactory. A new trial will be designed to answer the questions in the next phase.

Phase I clinical trial

In this phase, it is checked whether the drug is safe. They are usually the point where people first get involved. These studies are also helpful in deciding the best way to give a new treatment.

For this, side effects, tolerance, the best form of administration of the medication will be evaluated and safe doses will be determined as well as other aspects of the action of the drug in the human body.

Normally in this first phase, very few participants are involved, between 2 and 80 people approximately. Their number increases in subsequent phases, as more knowledge is gained about the drug or therapy.


Phase II clinical trial

In this phase, it is analysed if the drug works. That is, in addition to evaluating the safety, its effectiveness will also be determined.

For example, if it is to treat a disease, it will be tested in a limited number of people who have it. In this phase of the trial, 100 to 300 people usually participate and its duration is slightly longer than those of Phase I.

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Phase III clinical trial

In this phase, aspects of the safety and efficacy of the drug are verified, and if necessary, it is compared with other treatments used. In this phase, the drug is tested in a higher number of participants.

Which can range from 300 to more than 3,000. If the results obtained in this phase are sufficient and positive, the drug regulatory agencies can grant authorization and marketing of the drug with specific indications.


Phase IV clinical trial or follow-up studies

They examine the long-term effects once the drug has been marketed. These types of studies are used to monitor the effectiveness of the intervention, collect information on possible adverse effects associated with its widespread use or if it offers additional benefits.

There is no predetermined duration from when a drug is first tested. In subjects in phase I studies until it completes phase III and is approved for marketing by the competent body. Which in the case of Europe is the European Medicines Agency.

However, it is usually a long process between 10 and 15 years, in which factors such as the disease investigated. The type and duration of treatment and the number of participants involved intervene.




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