Commonly Used Terms

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This list was developed to provide easy-to-understand definitions of commonly used terms in clinical trials.

Randomized — The arm of the study (active treatment arm or placebo arm) that the patient will follow is determined by a flip of a coin (or like randomizing procedure).

Double-blind — Neither the patient, the treating physician, nor any other staff knows when or if the patient is receiving active treatment or placebo.

Placebo-controlled — Some patients exclusively receive the study drug or treatment and some patients exclusively receive a placebo, a harmless substance that has no effect and is used as a control.

Placebo crossover — Study includes a point whereby participants change study arms, although the timing of that change and whether drug or placebo is received remains blind to all. Some may take placebo for 4 weeks, have a 2-week wash-out with no drug or placebo, and then switch to taking taking the study for 4 weeks, for example. Others in the same study would begin with study drug for 4 weeks, 2-week wash-out and then cross over to take the placebo for 4 weeks.

Safeguards and Ombudsmen — Many checks and balances are in place to ensure safety.

  • New drug applications (NDA) are submitted to the Food and Drug Administration (FDA), requiring one or more pivotal Phase II trials. FDA oversight ensures maximal safety. Foreign studies may or may not help drug approval.
  • Further safeguards are placed by the Institutional Review Board (IRB) within the hospital or facility level where the ethical aspects and safety profile of the study are monitored on a regular basis.
  • The Data Safety Monitoring Board (DSMB) is comprised of independent experts in the field who have no part in the actual study, but are able to look at the unblinded progress of the trial and recommend changes in the protocol or even a premature discontinuation of the trial if warranted. Unintentional toxicity or data revealing continuation of giving the placebo over the actual medication is unethical give good cause to alter the study course.