Sant Joan de Déu Barcelona - Hospital
Clinical Trials Experience

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  • A clinical trial is a research project with human participation aimed to answer some specific questions about a new treatment (vaccines, new therapies or new indications of a known treatment).

    Medical research projects help to determine whether a given treatment is safe and effective. Clinical trials are carried out in different phases. Each phase has a different purpose and seek different objectives (for example, toxicity, adequate dose, etc.).


  • While clinical trials are generally research projects focused on the study of drugs, clinical research is a broader concept and it includes the study of medical devices (such as glucose meter), the evalution of a healthcare program or other iniciatives that are not directly linked to drugs. 

  • Los ensayos clínicos son diseñados por profesionales médicos o de la salud. Para diseñar un ensayo clínico, es muy importante considerar iniciativas de investigación previas y ciertas cuestiones relacionadas con el tratamiento y los síntomas que precisan ser abordadas para que se de una mejora. Los aspectos éticos son también cruciales.

    En el diseño de los ensayos clínicos hay diferentes participantes: médicos, enfermeras, pacientes, expertos en estadística y profesionales de apoyo, así como profesionales de la industria farmacéutica que colaboran para que el ensayo tenga el mejor diseño posible. El documento que recoge toda la información sobre el diseño del estudio se conoce como “protocolo”.

  • The aim of this phase is to study the security and toxicity of the new medicine. During this phase, the secondary effects that the drug may have on the health of the patient are considered (e.g. blood pressure rise).

    The number of participants in this phase is small and in the case of adults these are all healthy volunteers. In paediatric clinical trials, however, phase 1 only includes patients because it is considered unethical to expose a healthy child to any drug. 

    The number of patients in phase 1 range between 20-100.

  • In this phase patients participation is higher than in phase I (between 100 and 300).

    The goal of this phase is to study the effectiveness of a drug in relation to the possible secondary effects and the appropriate dose for the patient. In paediatric patients, this will be performed according to the different age groups.

  • This phase is iniciated once the security and effectivity results of the new drug are obtained from phases 1 and 2. The number of patients participating in phase 3 may range from 1,000 to 5,000. In phase 3 the drug is tested in relation to other existing treatments or to the placebo if there is no treatment.

    The duration of phase 3 is superior to phase 2 and may last a year.

    These kind of studies can be carried out simultaneously in different countries, thus, they are international studies in which different hospitals participate. 

  • Phase 4 is known as post-authorisation phase and it starts once the medicine is already in the market. Sanitary authorities require additional information from the pharmaceutical industry about the effects of the new drug in the “real world”. They also need to test the drug with more patients than those in Phase 3. 

    At this stage, security and effectivity data are obtained with patient subgroups, comparing the effect of the drug in combination (or not) with other existing treatments.

  • A blind or blinded-experiment is an experiment in which some information about the test is masked from the participants. These do not know if they are using the drug or a placebo. This methodology is employed in order to avoid any kind of bias until the trial has ended.

    There are several anonymization methodologies for the information associated to a clinical trial:

    • When the patient is not aware of the treatment he/she is receiving: single-blind.
    • When both the patient and the doctor/tester do not know the treatment: double-blind.



  • Unless circumstances are excepcional, it is strictly forbidden to include a patient in a clinical trial without the previous signing of a document confirming his/her acceptance. This document is called informed consent and confirms that the participant or his/her legal representative have received the essential information relative to the study in order to decide to participate or not.

    Informed consent is not a contract and it is possible to freely decide to abandon the clinical trial at any moment.

  • There are many clinical trials that use the randomization technique in order to select what kind of treatment should be administered to the patient reagarding the research methodology ( in comparison to a placebo or another treatment).

    Randomization is performed by a computer, not a medical professional, because this way it is easier to ensure equal opportunities for all participants to access the treatment and avoid any kind of bias.

    Using this technique helps to confirm that any outcome from he trial is completely objective and that it not a reflection of the particularities of the participants.

  • Bias are prejudices in favour of or against something, and it makes us wrongly conclude about the effects of a treatment. It is essential to detect any kind of bias in the biomedical research that may induce unsafe or ineficient studies, as well as the suspension of useful treatments.

    Researchers try to avoid bias using aleatorization and anonymization (blind), thus obtaining objective assessments in the evaluation of the studies.

  • "Inclusion criteria" are characteristics of the patients that help researchers to decide which ones are suitable candidates to participate in a clinical trial. For example, some studies only include patients of a certain age. In other cases it is necessary to perform some medical tests, such as a blood analysis, in order to validate the inclusion of the patient in the study.

  • "Exclusion criteria" are those criteria established by the researchers determining that a patient can not participate in a clinical trial. An example would be those studies excluding pregnant women in order to prevent risk of fetus damage.

    An exclusion criteria may also be taking any medication that may interact with the studied treatment.

  • In these kind of studies both the doctor/researcher and the patient know which treatment is being administered. In other words, we could say that this is an opposite situation to the doule-blinded trials.  

  • A placebo is a substance that has no effect on the patient. It allows researchers to study the “placebo effect”. This is a psychological response in which the patient starts to feel better although he/she has not taken any treatment with an active ingredient in it. 

    The comparison between the response of those patients that have taken the treatment and those who have taken the placebo helps researchers to analyze the benefits of the studied treatment.

  • The child can change his/her mind at any time during the running of the clinical trial nd he/she can leave any time he/she wants: before it starts, during the trial or during the follow-up process. Participation in a clinical trial is always voluntary.

    Quitting a study will not affect the doctor-patient relation.

  • It is possibe to have access to the information about the results of a trial once it has been completed. It should be considered that some studies involve thousands of people and that they could last for 5 years or more, exceeding the patient's participation period. 

    Thus, there could be a difference of time between the moment when a patient leaves the study and the moment when the clinical trial ends.

    Once the trial is finalized, the promoter (this can be a pharmaceutical company or a research centre) should make the results available to the participants. If someone is interested in this information, he could always ask the researcher or the patient's doctor about the conclusions of the trial.

    Results should always include information about the benefits and risks of the studied treatments. This information will help the patient and other patients like him/her to make better decisions about healthcare.

    Some researchers work with patient groups in order to ensure that the results of the trial reach those patients that have not participated in it. It is compulsory to publish the results of the trial although these have not been positive. This can be done via a medical congress, a scientific journal or the media.

  • Never. Actually it is usually all the way round. When somebody participates in a clinical trial the medical follow-up is very thorough and medical visits increase, increasing in turn the opportunities to share doubts with the doctor and the options to adquire more information about handling an illness.

  • With the purpose of ensuring that clinical trials meet standard ethical requirements, the majority of the studies meet those requirements established in the Declaration of Helsinki, which have additionaly been approved by the World Medical Organization. 

    The most important requirement established in the Declaration of Helsinki is the obligation to obtain obtener informed consent before participating in the clinicla trial.

  • It is recommended to talk to the doctor so he/she can assess whether someone is suitable to participate in a clinical trial.

    In order to obtain information about ongoing clinical trials there are public resources available. In our country, the resource of reference is Registro Español de Estudios Clínicos.

    Since 2011, the European Medicines Agency provides a website where all clinical trials carried out in Europe are published:

    In the United States of America there is a similar website that includes all clinical trials carried out around the world: