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Phase II Trials

Following Phase I clinical trials, Phase II research studies further evaluate dosage and safety while assessing the efficacy of the investigational drug. Unlike Phase I, Phase II clinical trials involve patients who live with the targeted condition for which the drugs are intended. From initiation to completion, Phase II trials can span one to several years.

Phase II Research: Who Participates?

Phase II clinical trials are conducted with patients who have the condition that the investigational drug is intended to treat or cure. Randomized groups of approximately 300 patients are typically used for Phase II research. Since the participants must have the targeted condition, the selection process for Phase II patients is stricter and more discerning.

Phase II Research: Why is it Conducted?

The second phase of the clinical study is important for a number of reasons. Phase II clinical trials can evaluate whether patients’ conditions improve with the administration of the investigational drug and if there are any side effects. Phase II research further assesses dosage and how much is most effective for treatment. In order to do this, patients are divided into two groups, only one of which will be taking the new drug. The other group, the control group, will be given a standard treatment, no treatment or a placebo. Since Phase II trials are double-blinded, neither the patients nor physicians are aware of the group receiving the actual treatment, reducing bias and increasing accuracy.

Common Questions:

What is a Clinical Research Trial?
Why Participate in a Clinical Research Trial?
Is there a difference between Clinical Trials and Treatment?

Learn More About Clinical Trials:

What Types of Clinical Trials are Available?
Phase III Clinical Trials
Phase IV Clinical Trials
Glossary of Clinical Trial Terminology
Alabama Health Resources
Brief History of Clinical Trials
Find Clinical Trials

Know Your Rights as a Participant:

Your Patient Rights
Patient Privacy Rules
Informed Consent Agreement
NIH Patient Bill of Rights
Legal, Ethical, and Safety Issues