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Clinical trials

A clinical research nurse taking the blood pressure of a volunteer.

A clinical research nurse taking the blood pressure of a volunteer.

Credits:Wellcome Library, London.

Through the ages, doctors have used different methods to test potential new cures. In the 1030s the Persian scholar Ibn Sina put forward rules for testing the medical effects of substances in his Canon of Medicine. However, a fundamental problem is that testing a drug on one person does not tell you very much. If you give a new drug to one patient, and he suffers side effects, maybe he is allergic to it - but other people might benefit from it.

It only became possible to carry out large-scale investigations with many patients when hospitals became places of medical research. Today drug companies developing new cures have to carry out different kinds of tests at various stages. Usually a substance is tested on animals before it is tested on humans in clinical trials. In these tests, some patients are given the new drug and others are given something else, either an older cure or a placebo. A placebo (Latin ‘I will please’) is a substance which has no known medical effect. With this measure, scientists can take into account the phenomenon that the patient's expectations may lead to improved health even if the administered substance is a sugar pill or something similar (the so-called ’placebo effect‘). Today clinical trials are usually ’double blind‘. This means that the new drug and the placebo are randomly assigned to patients, and neither the patients nor the scientists know who had received the drug or the placebo until after the trial. Following the principle of ’informed consent‘, experimental subjects at a clinical trial now have to be informed in advance that they may be getting a placebo.

Recently, AIDS activists and other patient activist groups have prompted researchers to dispense with the placebo group. This is to ensure that all patients receive treatment with a new drug which may turn out to be their last hope for a cure.


S Epstein, Impure Science: AIDS, Activism, and the Politics of Knowledge (Berkeley: University of California Press, 1996)

A Harrington (ed.), The Placebo Effect: An Interdisciplinary Exploration (Cambridge, Mass: Harvard University Press, 1997)