Multiple intracerebral hemorrhages in an elderly patient after adding quetiapine to a stable warfarin regimen

Drug Interactions Affecting Oral Anticoagulant Use

Oral anticoagulants (OACs) are medications commonly used in patients with atrial fibrillation and other cardiovascular conditions. Both warfarin and direct oral anticoagulants are susceptible to drug-drug interactions (DDIs). DDIs are an important cause of adverse drug reactions and exact a large toll on the health care system. DDI for warfarin mainly involve moderate to strong inhibitors/inducers of cytochrome P450 (CYP) 2C9, which is responsible for the elimination of the more potent S-isomer of warfarin. However, inhibitor/inducers of CYP3A4 and CYP1A2 may also cause DDI with warfarin. Recognition of these precipitating agents along with increased frequency of monitoring when these agents are initiated or discontinued will minimize the impact of warfarin DDI. Direct oral anticoagulants are mainly affected by medications strongly affecting the permeability glycoprotein (P-gp), and to a lesser extent, strong CYP3A4 inhibitors/inducers. Dabigatran and edoxaban are affected by P-gp modulation. Strong inducers of CYP3A4 or P-gp should be avoided in all patients taking direct oral anticoagulant unless previously proven to be otherwise safe. Simultaneous strong CYP3A4 and P-gp inhibitors should be avoided in patients taking apixaban and rivaroxaban. Concomitant antiplatelet/anticoagulant use confers additive risk for bleeding, but their combination is unavoidable in many cases. Minimizing duration of concomitant anticoagulant/antiplatelet therapy as indicated by evidence-based clinical guidelines is the best way to reduce the risk of bleeding.

Adverse events in children and adolescents treated with quetiapine: an analysis of adverse drug reaction reports from the Danish Medicines Agency database

Quetiapine is a low-affinity dopamine D2 receptor antagonist, approved for the treatment of bipolar disorder and schizophrenia in children and adolescents by the Food and Drug Administration, but not by European Medicine Agency. Although knowledge of adverse drug reactions in children and adolescents is scarce, quetiapine is increasingly being used for youth in Denmark. The aim of this case study is to discuss adverse drug events (ADEs) spontaneously reported to the Danish Medicines Agency on quetiapine used in the pediatric population in relation to adversive drug reactions (ADRs) reported in the European Summary of Product Characteristics (SPCs). The ADE report database at Danish Medicines Agency was searched for all quetiapine ADRs involving individuals (<18 years) in the period 1997-2015. Fifteen ADE case reports were retrieved, scrutinized, and categorized. The average age was 14.8 years (range 10-17 years) and six patients were boys. The main reported ADEs were (i) endocrine, for example, hyperprolactinemia and hyperthyroidism, (ii) cardiac, for example, tachycardia and QT prolongation, (iii) neurological, for example, seizures and cerebral hemorrhage, and (iv) psychiatric, for example, hallucinations. As some of the reported ADEs are life threatening and not listed as ADRs in the SPCs, off-label use of quetiapine in children and adolescents gives rise to safety concerns.