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Negative Control Drug or Negative Control Procedure:
Negative Control Drug or Negative Control Procedure:
A treatment incorporated into an experiment with the intention that it have no effects on the experimental system like those expected of the independent variable. In a pharmacologic experiment, the negative control drug mimics in every way the drug preparation under investigation (including identity of dosage form, vehicle, mode of application, etc.) except that the negative control drug lacks the ingredient that is expected to be responsible for the biological effect of the test preparation. The negative control drug has two functions in an experiment: 1.) To permit ascribing a causal relationship between treatment with the independent variable and changes in the experimental system which follow treatment. If the experimental system responds to both the negative control drug and the drug preparation under test, one cannot - in the absence of other information - legitimately infer that the effects of the test preparation are caused by the supposedly pharmacodynamically active test preparation. 2.) To serve as a basis for quantitative estimation of the effects of the independent variable in excess of those effects produced by non-specific changes in the environment or the experimental system. A test drug preparation may have non-specific effects like those of the negative control drug, but may also have specific effects that can be attributed to the ingredient that is unique to the test preparation.
Careful use of a negative control drug in an experiment prevents erroneous conclusions about the apparent activity of a test preparation; use of a positive control drug prevents making erroneous conclusions about apparent inactivity of a test preparation.
Cf. Positive Control Drug, Dummy, Placebo, Bioassay, Cross-Over Experiment
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