A new drug A is being compared with an old drug B, The efficacy of this new drug in relation to the old drug can be established by which phase of drug trial-
|B|| Phase II |
|D|| Phase IV|
Phase III of a clinical trial is regarded as full blown efficacy trial.
Some facts about the various phases of a clinical trial and their importance:
a. Phase I: Drug toxicity trials - done on "Healthy Volunteers" for side effects, tolerable dose of drug, drug availability and bio metabolism. Typically requires about 20-80 subjects or patients
b. Phase II: Initial clinical investigation for treatment effect - Done on patients + some healthy volunteers. Primary aim is to ratify the phase I findings, and also determine the dosage schedule and group of patients who are benefited by drug. Sample size 100 - 200.
c. Phase III: Full Scale evaluation of treatment - Comparing with standard regimens and/or placebo synonymous with "Clinical Trials".
d. Phase IV: Post Marketing Surveillance - Done after 'Drug' launched for large scale data on efficacy, safety, and long term side effects etc.
e. Phase V: Re-efficacy trials. This is seldom done. Usually high degree of adverse effects from data in phase IV is the driving point for these.