Clinical Trial Lingo: Blind, Phase, Placebos

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Category: Research Articles Published on Monday, 01 August 2005 Written by Yong Tsai, MD
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The possibility that a treatment results occur by chance alone is not an acceptable answer when it comes to patient care, which is why clinical trials and research have become an essential factor in finding the best treatment for the patient.

Classed within four phases, clinical trials can provide statistically significant answers to specific health questions, via data collected from human volunteers, in regards to the effects of a particular treatment.

Phase I studies the effects of a new, non-FDA approved or experimental drug or treatment in a small group of healthy people (20-80). This phase is primarily concerned with assessing a drug’s safety and how the body absorbs, metabolizes, and excretes it. Testing usually lasts several months with about a 70% pass rate, and an end result of an established dose range and an insight of possible side effects.

Once the treatment has been deemed safe, a Phase II trial is initiated to determine its efficacy: This second phase of testing may last from several months to two years, and usually enrolls up to several hundred patients who have the disease for which the treatment was developed. Only about one-third of these experimental drugs successfully make it passed this, more intense phase of testing.

For the promising treatments that moved onto the final pre-approval stage, Phase III trials compare the new treatment to the current standard treatment, while confirming its safety and efficacy and monitoring side effects. Usually, the subject pool consists of 1000 to 3000 patients, for up to several years, with a pass rate of 70 to 90 %. Once this phase is successfully completely, a pharmaceutical company can request FDA approval for drug marketing.

After a receiving FDA approval, Phase IV trials or “post-marketing studies” can be conducted to compare it to other similar treatment, to study further risks or benefits, and to determine its optimal use.

For further statistical significance, clinical trials often compare the actual drug to a placebo. An important part of scientific research, the “placebo effect” is a phenomenon that causes 20 to 30% of people who unknowingly take a "sugar pill," or a substance with no medicinal content, to report improvement. Even though the exact source of a placebo's power is unclear, experts believe it to be related to the mind-body interaction and positive thinking. Further processes like single-blinding (subject unaware if they receive drug or placebo), double-blinding (subject and investigator, coordinator, and sometimes monitors unaware) can provide additional assurance against bias results.

Because the placebo-effect response can mislead the untrained eye, these results must be taken into consideration when determining a treatment’s true benefit, efficacy, and safety. If a study proves that 40% of the participants had significant improvement after treatment, what percentage are a result of drug efficacy or simply of the placebo-effect?

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