Inhibition is important from the therapeutic point of view since many substances designed to be used as drugs against some diseases can eventually have an inhibitory side effect on other enzymes. For example, Paracetamol is an inhibitor COX-3 cyclo-oxygenase [20], preventing the formation of arachidonic acid into prostaglandins, which are involved in pain and fever process. Paracetamol is transformed by the cytochrome P450 dependent enzymes producing N-acetyl-p-benzo-quinone imine (NAPQI), which is normally conjugated with glutathione for renal elimination. In case of overdose the glutathione production pathways are not able to produce enough glutathione and NAPQI, which is very reactive, accumulates in the liver leading to its failure [21]. Hence, any system able to predict the inhibitory effect of substances on the metabolic network would be useful in assessing the potential harmful side effects of drugs.