The objective of the present investigation work was of identifying, to quantify and Tipificar the interactions potential present medicamentosas in the medical precripciones of the Neurosurgery of the National Hospital Edgardo Rebagliatti Martins. The present investigation work is a study decriptivo, traverse and retrospective, for the one which, 2982 were analyzed you prescribe patients medicas hospitalized in the service of Neurosurgery of H.N.E.R.M, in the period of February. Julio the 2007, of these, 2912 fulfilled the inclusion approaches, which were subjected to evaluation to determine the interactions medicamentosas, by means of the bibliographical method. analytic, being at the end, 1495 recipes with interactions potential medicamentosas. It was found that 51,34% of the recipes presented interactions potential medicamentosas, among the most frequent: Phenytoin – Ranitidine (18,9...