Primary and secondary nonresponse to infliximab: mechanisms and countermeasures.

INTRODUCTION: Primary and secondary non-response to infliximab are common in patients with inflammatory bowel disease and remain a management challenge in clinical practice. Areas covered: This article describes the epidemiology, mechanisms and risk factors for primary and secondary nonresponse to infliximab in patients with inflammatory bowel disease. Data on proactive and reactive therapeutic drug monitoring are examined in this review. An algorithm for evaluation and management of non-response to infliximab is provided. Preventative measures are also discussed. Relevant articles were identified after a literature search using PubMed. Search terms included 'infliximab', 'loss of response', 'immunogenicity', and 'drug monitoring'. References of identified articles were also reviewed to identify additional references. Expert opinion: A common cause for primary and secondary non-response include inadequate dosing of infliximab; inadequate dosing can be identified through assessment of drug and anti-drug antibody levels. Therapeutic drug monitoring should be done in patients losing response to infliximab. Use of drug monitoring proactively is still under debate.