Clinical Research Trials

Double Blind Placebo Control Study

Welcome to Clinical Research Trials - There are some other techniques for medical research that can be employed besides the therapeutic trials. These include double blind and single blind techniques, placebo control, parallel groups. We can further evaluate pharmacoepidemiological aspects as The Observational Cohort Study and Case Control Study along with Record linkage by computers.

The Measurable Difference By Clinical Research Trials:

Definitive Therapeutic trials are expensive, tedious and time consuming. Sometimes when the result comes, that can even be useless or vague in nature. Again the single trial will seldom give a conclusive answer to a therapeutic question. Confirmatory trials by other persons in other centers are needed to reach reasonable certainty.

Meta Analysis Of Clinical Research Trials:

When numerous trials have been done and results vary, it is necessary to do meta- or overall analysis. Simply an addition of results won't solve the dilemma. However it should be remembered that the selected trials should be of high value.

Double Blind & Single Blind Techniques In Clinical Research Trials:

W. Modell in JAMA (1958; 167: 2190) describes the double blind technique, "This is a control device to prevent bias from influencing results. On the one hand it rules out the effects of hopes and anxieties of the patient by giving both the drug under investigation and a placebo or dummy of identical appearance in such a way that the subject (the first blind man) does not know which he is receiving. On the other hand, it also rules out the influence of preconceived hopes of, and unconscious communication by, the investigator or observer by keeping him (the second blind) ignorant of whether he is prescribing a placebo or an active drug. At the same time the technique provides another control, a means of comparison with the magnitude of placebo effects. This device is both philosophically and practically sound."

A non-blind clinical research trial is called an 'open trial'.

The double blind technique should be used when evaluation depends on other than strictly objective measurements. Like the pain in Rheumatoid arthritis may look as objective but closer look may prove it to be subjective.

Sometimes the double blind technique is not possible like the side effects of an active drug reveal which patient is taking the active drug.

Placebo Medication As A Control In Clinical Research Trials:

Dummy or Placebo treatment is used with double blind technique. Its use is not invariably necessary nor indeed ethical. It is not permissible to deprive patients of effective therapy. But it is often preferable to discontinue the use of unproven efficacy or safety. Frequently, consent may be obtained to the use of placebo without impairing the scientific validity of the procedure.

The Use Of Placebo In Clinical Research Trials:

• Placebo helps in identifying the beneficial effects of a drug from the psychological effects of taking the medicine and the surrounding circumstances like increase interest by the doctor, more frequent visits etc.

• It establishes the drug effects from fluctuations in disease that occur with time and other external factors when the active treatment is witheld.

• It helps to avoid false negative conclusions.

Parallel Groups:

Within Patient Group Parallel Study:

In Chronic stable diseases with no cure but with alleviation of symptoms alone,  each of the treatment including placebo is given to each patient. In this way we use them as their own controls. It is important to ensure in a small series that each drug both precedes and follows each other drug the same number of times to avoid the risk of carry over effect. This study has some drawbacks like presence of a drug or metabolite and enzyme induction.

So Between Patient Group parallel studies are preferred. And they require large number of patients.

Further in acute self-limiting diseases, it is impossible to give more than one treatment to one patient. So the controls should be other patients.

The Historic Controls In Clinical Research Trials:

When the treatment is given to all patients of present group and it is compared with the past studies is called the historical controls. It is unacceptable for standards of treatment and diagnosis change, severity of diseases fluctuates.

The following table is taken from 'Measurements in Rheumatoid Arthritis' by Hart F. D. et al 1972.

Pharmacoepidemiology in Clinical Research Trials:

Three epidemiological approaches are used to determine the results of controlled therapeutic trials for performance of the treatment in community medicine. These are observational in nature in place of experimental.

The Observational Cohort Study:

In this forward looking or prospective study, all the patients taking the drug are collected and followed up to determine the outcomes - both therapeutic and adverse. Prescription event monitoring is an example where patients are observed after writing the prescription. The major trouble with this study is selection of an appropriate control group, the need for large number of patients, and prolonged surveillance.

The Case Control Study:

In this backward looking or retrospective investigation, the investigator assembles a group of patients who have the desired condition. Then a control group of patients who have not had an episode of the particular condition is assembled like from similar age, parity, smoking habits from hospital admissions, primary case records. Both groups are followed retrospectively.

The Observational method is cumbersome, expensive and can't satisfy the urgent need for an answer after a doubt is raised. A case control study is done quickly with smaller number of patients. The disadvantages of case control study are the possibility of suspicion of intrusion of unknown and unavoidable biases in selection of patients and controls. Further it requires a definite suspicion of causality. So these don't prove causality. They reveal only associations.

Clinical Research Trials & Record Linkage By Computers:

This allows correlation of Clinical Research trials in a population of life and health events with history of drug use. It is being developed as far as resources permit.

Reliability Of Published Clinical Research Trials:

In one published study it was reported that about 66% of published papers are acceptable and 33% unacceptable according to what are now generally agreed criteria.

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The Preclinical or Animal Research studies - discovery to development of medicine - Its role in Herbal Research.

The Therapeutic trials  in Man - Its role in Clinical research trials of Herbal  Research.

How the Therapeutic Clinical Research trials are designed and What are the ethics of research in man? How are they sized appropriately?

What is double blind clinical research trials? Why are they necessary?

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