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2.Phases of Clinical Trial:
a . phase 0
b . Phase 1
c. Phase 2
d . Phase 3
e . Phase 4
Any investigation in human subjects
intended to discover or verify the clinical,
pharmacological, and other pharmacodynamic
effect of an investigational product and to identify
any adverse reactions to an investigational product,
and to study absorption, distribution, metabolism,
excretion of an investigational product with the
object of ascertaining its safety and efficacy.
Phases of clinical trial
• Phase 0 is a recent designation for exploratory, first-in-human
trials conducted in accordance with the United States Food and
Drug Administration's (FDA) 2006 Guidance on
Exploratory Investigational New Drug (IND) Studies. Phase 0
trials are also known as human micro dosing studies.
Distinctive features of Phase 0
Primary goal:- Pharmacodynamic and Pharmacokinetic
particularly oral bioavailability and half-life of the drug.
Dose: it is 1/100th of therapeutic dose.
Subjects: 10-15 healthy volunteers.
A Phase 0 study gives no data on safety or efficacy, being by
definition a dose too low to cause any therapeutic effect.
Phase 0 clinical trial are not mandatory. They are case to
Phase I trials are the first stage of testing in human subjects.
Normally, a small group of 20–100 healthy volunteers will be
Phase I trials also normally include dose-ranging, also called
dose escalation studies, so that the best and safest dose can be
found and to discover the point at which a compound is too
poisonous to administer
Distinctive features of Phase 1
Primary goal: To assess the safety (pharmacovigilance),
tolerability, pharmacokinetics, and pharmacodynamis of a
These trials are often conducted in an inpatient clinic, where
the subject can be observed by full-time staff.
Phase I trials most often include healthy volunteers.
The tested range of doses will usually be a fraction of the
dose that caused harm in animal testing.
Volunteers are paid an inconvenience fee for their time spent
in the volunteer centre. Pay depends on length of participation.
Different kinds of phase1 trial
Once a dose or range of doses is determined, the next
goal is to evaluate whether the drug has any
biological activity or effect. Phase II trials are
performed on larger groups (100-300) and are
designed to assess how well the drug works, as well
as to continue Phase I safety assessments.
Types of Phase 2
Distinctive features of phase 2a
Primary goal: To determine the therapeutic efficacy.
Pilot trials: Dose response determination, determine
dose regimen and determination of target population.
Subjects: Few hundreds . Patients fitting narrow
Trial design: Comparison with baseline status. Open
level or single/ double-blind.
Parallel dose response.
Distinctive features of Phase 2b
Objectives: Focus on aspects of phase 2a trial.
Placebo or other concurrent control.
Subjects: similar to phase 2a.
Trial design: Single or double blinded.
Conducted at multiple sites.
Phase III studies are randomized controlled multicenter
trials on large patient groups (300–3,000 or more
depending upon the disease/medical condition
studied) and are aimed at being the definitive
assessment of how effective the drug is, in
comparison with current 'gold standard' treatment.
Types of Phase 3
Trial design: open level or
single or double blinded.
Testing different stages
of the disease indication.
Dosage forms , formulation
Phase 3b: Phase III trials will
continue while the regulatory
submission is pending at the
appropriate regulatory agency.
This allows patients to continue to
receive possibly lifesaving drugs
until the drug can be obtained by
purchase. i.e. Antiretroviral,
Phase IV trial is also known as post marketing surveillance Trial. Phase IV
trials involve the safety surveillance (pharmacovigilance) and ongoing
technical support of a drug after it receives permission to be sold. The
safety surveillance is designed to detect any rare or long-term adverse
effects over a much larger patient population and longer time period than
was possible during the Phase I-III clinical trials. Harmful effects
discovered by Phase IV trials may result in a drug being no longer sold, or
restricted to certain uses: recent examples involve cerivastatin (brand
names Baycol and Lipobay), troglitazone (Rezulin) and rofecoxib (Vioxx).
Clinical trial may occur in several different phases .
Drug are developed in several different phases to
meet the multiple objective in the safest, most
efficient manner. Phase is only a description and
not a set of rules.