Alternative methods

What are alternative methods to animal testing?

According to the recent estimates, in the European Union alone, approximately ten million vertebrate animals are slaughtered for different experimental purposes (i.e., scientific, toxicological, regulatory, etc.). This is so because the efficacy of many chemical substances – e.g., pharmaceuticals, pesticides, food excipients, cosmetics, etc.- has traditionally been determined through the use of living beings. In addition, a good part of the regulatory entities that authorize the commercialization of new products require very detailed studies of the potential toxic effects of these products on humans and the environment.

Types of experimental animals used in the EU. 


The high number of slaughtered animals has a moral component and an ethical impact on our society, which we are increasingly aware of. This has led to the generalization of a collective desire to end such experiments. Along these lines, Russell and Burch already postulated in 1959 a principle that is still followed today, according to which animal experiments should only be accepted when the so-called “3 Rs” (replacement, reduction and refinement) criteria have been previously applied. Basically, they propose that, before considering the use of animals, we must try to replace traditional tests with alternative methods or “new approach methodologies” (NAMs), which allow the same results to be obtained through techniques that do not involve the use of living beings. When this is not feasible, the number of animals used should be reduced as much as possible, and experimentation techniques should be refined to minimize the pain or discomfort that these animals may suffer. The use of alternative methods is no longer simply a social aspiration. Instead, various international regulatory entities have introduced them into their regulations, clearly establishing that the testing of chemical products on animals should be considered only as the last option, when there is no other scientifically reliable alternative to demonstrate the impact of these products on humans or the ecosystem.

As we have seen, the first (and most important) of the ‘3 Rs’ criteria is the replacement of animal tests by other methods. Several alternatives exist, such as the replacement of vertebrate animals with less complex organisms (bacteria, algae or fungi), or the use of so-called in vitro techniques, which, unlike animal tests (known as in vivo tests) do not use whole animals, but portions of tissues, isolated organs, or cell cultures. These alternatives also include computational or in silico methods, which allow the simulation of mechanisms of action and the prediction of human or environmental toxicity through the use of models based exclusively on computer algorithms and computational modeling.

In silico techniques have several advantages over all the other methods, fundamentally their ability to predict the physical-chemical or biological properties of compounds in a much faster way, allowing the screening of thousands of chemical structures in minutes / hours, versus  in vitro tests (days / weeks) or in vivo (weeks / months), as well as a great reduction of costs and other resources. Computational studies also have the advantage that they are executed with “virtual” structures, in that it is not necessary to carry out chemical synthesis in the laboratory. In this way, a company or researcher that wishes to know the effects or toxicity of a compound can do so prior to its synthesis, which is only carried out if its interest and safety is confirmed.

In short, the use of computational approaches is characterized by its easy and immediate applicability to new structures, and represents a very significant saving of time, resources and money. In the next entries of this blog we will tell you how these methods work, their interest and the great possibilities that they offer.


[1] Statistics on the use of animals for scientific purposes in the Member States of the European Union and Norway in 2018. Summary Report, European Commission. and

[2] Russell, W.M.S. & Burch, R.L.. (1959). The Principles of Humane Experimental Technique. Methuen and Co LTd. London.

[3] Gozalbes, R., de Julián-Ortiz, J. V., & Fito-López, C. (2014). Métodos computacionales en toxicología predictiva: aplicación a la reducción de ensayos con animales en el contexto de la legislación comunitaria REACH. Revista de Toxicología31(2), 157-167.