> In Silico Method

In silico toxicology began in the 70’s and 80’s.

Much of the progress made in this field was accelerated by the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) legislation in Europe. One of its mandates is to promote alternative  methods to reduce the reliance on live animals in chemical testing.

The in silico method can be interpreted as testing that involves a computer or use of computer simulation in experimental research.

Common ways that in silico methods are incorporated into experiments are:

  • Planning experiments and power analysis: computer tools are used to improve the design  of in vivo and in vitro experiments.
  • Data analysis procedures: a computer is typically used for statistical analysis in an experiment.
  • Prediction models: algorithms are used to translate an in vitro outcome in an experiment to predict the expected outcome for an in vivo test.

Other uses of computational toxicology that involves the computer more extensively rather than using it as a supplement are:

  • Expert systems: parameters are systematically defined and applied by software to a compound of interest to make certain predictions.
  • Quantitative structure-activity relationship (QSAR): software can be developed to predict the structure and activity relationship in certain biological systems.
  • Modelling tools: three dimensional models are used to model a receptor in the body and new structures are tested to see if they can fit to it. The kinetics of substances can also be modeled to predict what happens to a substance over time in the body.


The European Chemicals Bureau and the Organization for Economic Cooperation and Development are compiling a database and creating QSAR risk assessment models. QSARs are models that can predict the physicochemical and biological properties of molecules. Research involving new and existing chemicals can use this database to predict:

  • physiological properties
  • environmental fate
  • ecological effects
  • human health effects.


The pharmaceutical industry benefits greatly from this database because they can screen chemicals that is already known to cause adverse properties to accelerate the drug discovery process.

In silico methods also benefit the cosmetic industry. Software such as Tissue Metabolism Simulator (TIMES) software is a skin sensitization model. It incorporates skin metabolism and examines the reaction of the testing chemical with the skin proteins. Skin metabolism and the interaction of the chemical with the skin can be simulated and the structure-toxicity and structure-metabolism relationships can be observed with this model.

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