**5. Cost of adverse drug reactions**

In western countries, drug-related illnesses account 5% to 10% of inhospital costs, and being associated with a substantial increase in morbidity and mortality. In addition to their impact on human health, ADRs also have significant impact on healthcare costs. These costs are essentially hospital costs, in particular arising from an increase in length of stay caused by an ADR. Although has been estimated that the occurrence of an ADR during hospitalization or leading to hospitalization is responsible in U.S.A. (data from 1997) for a cost of approximately 2800 Euros in an additional length of stay of 2.2 days, several studies have also pointed out that the structure of ADR cost is heterogeneous, a factor which must be taken into account when developing preventive strategies. Although data of costs were not calculated, Sanchez Muñoz-Torrero et al (2010) study found an increase in hospital staying in almost 9 days (18±17 days vs 9.6±5.8, p<0.001), which accounts for more direct and indirect costs of the hospitalization. Also another Spanish (Carrasco Garrido et al, 2010) study found an increase in 19% of hospital costs associated with the appearance of adverse drug events.
