There is a wide range of alternative methods intended to replace animal testing. Why are they not used more often by researchers?

Multiphoton fluorescence image of HeLa cells stained with the actin binding toxin phalloidin (red), microtubules (cyan) and cell nuclei (blue)
Immagine: National Institutes of Health (NIH)

Whenever researchers apply for permission to conduct an animal experiment, they are required to explain why they are not using methods that do not involve animals. No animal experiment may be conducted if an alternative method is available and suitable "based on the latest state of knowledge" (see Animal Protection Ordinance) to achieve the purpose of the experiment.

There is no "either/or": Researchers are not working either with the use of animals, or with alternative methods. Normally, both approaches are combined, by conducting investigations without animals alongside studies involving animals, if required. For example, artificial organs are an alternative method, the results of which, are often supplemented with those from an animal experiment. The effect of a substance on an organ can in part also be tested in a tissue or cell culture experiment. However, interactions within the body can only be evaluated properly with an animal experiment; they are critical with respect to the side-effects of medications. The effect of a heart medication is different on isolated cardiac tissue than when it interacts with the liver, where part of the drug is broken down or modified.

A body, whether human or animal, consists of different organs and cell types, which are connected in multiple ways through complex systems. As a result, it is virtually impossible to draw conclusions from studies of individual cells or tissue cultures on the effect of an active ingredient in the entire organism.