[Reactions to drugs. A review of literature]

Adverse drug reactions are originated by immunological and non-immunological mechanisms. Estimated incidence is of 6.7%, and the incidence of mortal reactions is of 0.32%. In women, skin reaction incidence is 35% higher than in men, and it is 20 times higher than presenting contrast medium-related reactions. Allergic reaction is classified accordingly to Gell and Coombs criteria. It is unknown the pathogenic mechanism of the drug-induced fever. Predictable reaction depends on the dose and it is frequently related to the drug. Unpredictable reaction depends on the individual and pseudoallergic features of each patient; no immunological mechanism is involved. For diagnosis, lymphocyte transformation test measures the T cell proliferation to an in vitro drug; furthermore, it is the most sensitive. There are just a few options to evaluate and manage those patients. When it is impossible to make the exposition test the alternative is to withdraw the drug and try another treatment option. If there is no other available drug, desensitization must be considered.