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An active placebo is a placebo that produces noticeable side effects. This is in contrast with a passive placebo, which has no side effects. The purpose of an active placebo is to reduce unblinding in blinded experiments.

Relevance to clinical researchEdit

When a treatment has side effects while the control does not, patients who experiences side effects may correctly guess that they are receiving treatment. If patients are able to discriminate between treatment and placebo at a rate greater than chance, the experiment is not truly blind. This introduces bias in favor of the treatment group and may lead to a type I error.[1]


A 2005 study used lorazepam as an active placebo to test morphine and gabapentin for efficacy in the treatment of neuropathic pain.[2]


  1. ^ Altman, Douglas G.; Day, Simon J. (19 August 2000). "Blinding in clinical trials and other studies". BMJ. 321 (7259): 504. doi:10.1136/bmj.321.7259.504. ISSN 0959-8138. Retrieved 20 April 2019.
  2. ^ Gilron I, Bailey JM, Tu D, Holden RR, Weaver DF, Houlden RL (March 31, 2005). "Morphine, gabapentin, or their combination for neuropathic pain". N Engl J Med. 352 (13): 1324–34. doi:10.1056/NEJMoa042580. PMID 15800228.