1. Animals should be replaced by less sentient alternatives such as invertebrates or in vitro methods whenever possible.
  2. Experimental protocols should be refined to minimize any adverse effects for each individual animal. For example, appropriate anesthesia and analgesia should be used for any surgical intervention. Death is not an acceptable endpoint if it is preceded by some hours of acute distress, and humane endpoints should be used whenever possible (Stokes 2000). Staff should be well trained, and housing should be of a high standard with appropriate environmental enrichment. Animals should be protected from pathogens.
  3. The number of animals should be reduced to the minimum consistent with achieving the scientific objectives of the study, recognizing that important biological effects may be missed if too few animals are used. Some thought also should be given to the required precision of any outcomes to be measured. For example, chemicals are classified into a number of groups on the basis of their acute toxicity in animals. It may not be necessary to obtain a highly precise estimate of the median lethal dose (LD50 value) to classify them. A number of sequential experimental designs that use fewer animals have been developed for this purpose (Lipnick et al. 1995; Rispin et al. 2002; Schlede et al. 1992). Ethical review panels should also insist that any scientist who does not have a good background in experimental design and statistics should consult a statistician.