Written by Vanessa Jones, B.A  | 
Medically Reviewed by Dr. Sunil Shroff, MBBS, MS, FRCS (UK), D. Urol (Lond) on Aug 28, 2014

Clinical Trials - Phase III

There can be different types of Phase III trials:

  • Randomized trials
  • Open trials
  • Factorial trials
  • Crossover trials
  • Orphan drug trials

After obtaining adequate evidence from a Phase -II study regarding the effectiveness of a new drug / treatment, the next step is a Phase -III trial.

The purpose of a Phase -III trial is to gain additional information regarding the effectiveness and safety that is required to evaluate the overall benefit - risk ratio of the new drug / treatment. It is usually performed in a larger group of individuals (1000 -3000). All patients in phase III studies are closely watched. The study will be stopped if the side effects of the new treatment are too severe or if one group has had much better results than the others.

Some Phase III trials, combine both Phase I and Phase II trials into a single trial,inoder to monitor both the effiasy and toxicity of the new drug / molecule.

  • Randomized trials
  • Open trials
  • Factorial trials
  • Crossover trials
  • Orphan drug trials

A clinical trial that involves at least one test treatment and one control treatment, in which the treatments administered are selected by a random process (eg, coin flips or a random-numbers table).In randomized trials, individuals are randomly assigned either group of treatment. One group (the control group) receives the standard (most accepted) treatment and the other group receives the new treatment.

Blind Trials

The idea behind conducting blinded studies is to prevent conscious and unconscious bias in research.

Single - blind trial / Single masked trial

A single blind trial is a study in which the investigator is aware of what treatment the patient is getting but the participant is unaware of the medication taken. This trial has both its advantages and disadvantages. Since the patient does not know which treatment is being administerd, it minimizes the placebo effect. However since the researcher is aware of the medication the participant is receiving, they might tend to treat the patient differently or unknowing tell the patients crucial treatment related details that could effect the studies outcome - known as the experimenters effect.

Double blind trial / Double masked trial

A double blind study is one where neither the individual participating in the study nor the study staff knows which participants are receiving the experimental drug and which are receiving a placebo (or another therapy).

In a double blind study the sponsor (or research person) allocates a series of numbers to " The experimental / New treatment" or "Old treatment". The Principal Investigator / Study Co-ordinator is told the numbers, but not what they have been allocated to.

Since the second researchers are not aware of the treatment being given to the patient they will not be able to influence the patient. For this reason double-blind (or randomized) trials are preferred when compared to single blind studies as they eliminate subjective bias on the part of both experimental subjects and the experimenters.

Triple -Blind trial / Triple masked study

In a triple blinded study the researcher / the drug company, the doctor administering the treatment and the subject are unaware of what is being given. An advantage of a triple blind study is that it prevents undue influence of study results by anyone directly involved in the study.

Controlled trials

Control is a standard against which experimental observations may be evaluated. One group of participants are given an experimental drug, while the other group (i.e., the control group) is given either a standard treatment for the disease or a placebo.

Uncontrolled trials

Research studies in which there are no participants taking a placebo.


It is usually a tablet, capsule, or injection that contains a harmless substance but appears to be the same as the medicine being tested, but a substance of no medical value.


jagan1206 Wednesday, January 7, 2015

can any one give me different names given to different phases in clinical studies?

infoalcpl Friday, October 29, 2010

My colleagues and I have just concluded one of India's most in-depth studies on "Clinical Trials in India". We have looked at various areas such as:
- Market Trends
- Growth Drivers
- Regulatory Bodies and Framework
- Major Players.
We interviewed over 200 individuals and firms to collect the data in what we believe is one of the most detailed study on the subject in India.

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