Abstract : Some patients are exposed to complex clinical situations, which impose a careful analysis of both the indi-cations and contra-indications of ongoing pharmacological treatments as well as of the dosing or drug adjustments to be proposed. This article illustrates some problems encountered when a new drug therapy is initiated, when medications with narrow therapeutic window should be supervised and when some drugs should be stopped mainly for safety reasons. The clinical case relates the story of a patient with type 2 diabetes, arterial hypertension and coronary heart disease, who presents a congestive heart failure associated with an episode of atrial fibrillation and a severe renal insufficiency.