Phases of clinical trials

Clinical trials can only be done if that particular drug is found to be safe in various preclinical studies. Preclinical studies are conducted on various animal species to test any carcinogenic, teratogenic or mutagenic potential of a particular drug. When a particular drug is found to be safe in preclinical studies then regulatory bodies give approval to conduct clinical trial.
Clinical trial consist of four phases. In phase I drug is tested on normal human volunteers to know about pharmacokinetics and pharmacodyanamics of that particular drug. In phase II drug is tested on both healthy volunteers as well as patient to know the safety and efficacy of that particular drug. In phase III drug is tested on patients to know about safety and efficacy of that drug but in phase III sample size is relatively larger as compared to phase II. In phase IV or post marketing surveillence phase any adverse effect is supervised on large sample of population to know about any rare side effect.

Types of clinical trial

Clinical trials can be of various types such as open label or blinded trials. Blinding is done to eliminate various types of bias that is why double blind randomized clinical trials are considered as gold standard. Blinding may be of various types. In single blind studies patient does not know whether he belongs to control group or test group. In double blind studies both the participant and phycisian do not know about group allocation and only third party know about group allocation. Clinical trials may be placebo controlled or standard controlled. Placebo is an inert pharmacological substance which has no activity of its own. Placebo can be used only only after ethical approval. Placebo can be used only under certain circumstances such as when the disease is not very serious or there is no alternative effective treatment is available.

What is a clinical trial ?

A clinical trial is a scientific and rational method of testing any diagnostic, prophylactic or therapeutic effect of any new chemical substance or a drug on human beings. It is conducted under strict supervision of various legal and ethical guidelines. Because clinical trial may involve normal healthy volunteers so it should be conducted under according to norms and regulations of various ethical guidelines.
During world wars various inhumane and crual methods are adopted on prisoners of wars to test any new hypothesis or natural history of various infectious diseases or any new drugs. Keeping in mind these things various regulatory bodies were formed which form rational guidelines regarding trials in which healthy human beings were used.

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