Environmental factors, Good

A good clinical trial is designed to take account of the variability in response (either efficacy or adverse event) that is expected when a new active drug is tested. This response depends on an individual s genetic make-up, and on a number of environmental factors, such as disease state, other drugs and age. The size of the trial and the selection of study subjects are carefully determined to reduce the variability in response to a minimum (i.e. to maximise the sensitivity of the trial) so that the trial endpoints can be determined with as much certainty as possible. 

Good animal care is critical at all times because toxicity has been shown to vary with diet, disease, and environmental factors. Animals should be quarantined for some time before being admitted to the test area, their diet should be optimum for the test species, and the facility should be kept clean at all times. Regular inspection by a veterinarian is essential, and any animals showing unusual symptoms not related to the treatment (e.g., in controls or in low dose but not high dose animals) should be removed from the test and autopsied. 

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